IRLF 


I 


1 


REESE  LIBRARY 


UNIVERSITY    OF    CALIFORNIA. 


Received 
Accessions  No. 


•  .Vie//  ,\v> 


•    . 


A  TREATISE 


PRACTICAL  AND  THEORETICAL 


MINE    VENTILATION. 


BY 


EUGENE   B.  WILSON, 

INSTRUCTOR   IN   DRIFTON   INDUSTRIAL   SCHOOL   FOR   MINERS 
AND   MECHANICS. 


NEW  YORK : 

JOHN     WILEY     &     SONS, 
15   ASTOR   PLACE. 

1887. 


COPYRIGHT,  1884, 
BY  EUGENE  B.  WILSON. 


JFranfeltn 

RAND,   AVERY,   ANC  COMPANY, 
BOSTON. 


PREFACE. 


THE  author,  aware  of  the  interest  manifested  by  miners 
in  this  subject,  which  is  so  intimately  connected  with  their 
daily  employment,  has  endeavored  to  deal  with  ventilation 
in  such  a  manner  that  no  one  with  a  fair  knowledge  of  the 
English  language  and  of  arithmetic  need  despair  of  thor- 
oughly mastering  it. 

Knowing  that  the  miner  possesses  but  a  comparatively 
small  stock  of  words,  and  is  not  an  adept  in  algebraic  for- 
mulas, the  writer  has  taken  a  different  position  from  the 
standard  works  on  the  subject,  endeavoring  to  do  away  with 
abstruse  language,  and  such  highly  mathematical  formulas 
as  are  only  calculated  for  well-educated  engineers.  In 
order  that  the  text  may  be  more  readily  followed,  each  arti- 
cle is  illustrated  b}'  an  example.  From  the  number  of  fatal 
explosions  which  have  taken  place  within  the  past  eighteen 
months,  it  is  evident  that  either  managers  are  ignorant  of 
the  laws  of  ventilation,  or  else  negligent  in  providing  methods 

iii 


IV  PREFACE. 

in  conformity  with  those  laws.  If  the  latter  is  the  case,  they 
are  the  more  blamable ;  as  ignorance  of  the  subject,  even  at 
this  time,  may  be  excusable,  but  negligence  can  never  be. 
There  are  many  practical  hints  given  for  engineers,  who, 
owing  to  lack  of  time,  have  been  unable  to  keep  as  well 
informed  on  this  subject  as  they  may  have  wished  to  do : 
also  many  useful  memoranda,  and  tables  for  saving  time  and 
labor  when  dealing  with  questions  relating  to  ventilation, 
will  be  found  in  this  little  volume. 

The  author  would  also  state,  that  this  book  is  intended  for 
miners,  and  not  for  engineers  ;  but  at  the  same  time  it  is 
believed  that  it  will  be  found  useful  to  many  engineers. 

In  hopes  of  showing  how  men's  lives  may  be  lengthened, 
and  preserved  from  the  dangers  that  lurk  in  improperly  ven- 
tilated mines,  this  work  has  been  written,  and  is  now  offered 
to  the  class  most  interested,  by  their  friend  and  well-wisher, 

E.  B.  W. 

DRIFTON,  PENN.,     une,  1884. 


CONTENTS. 


CHAPTER  I. 

PAGE. 

§1.    Atmosphere.— Specific  Gravity  of  Gases  .  1 

§  2.    Nitrogen 5 

§  3.    Oxygen 7 

§  4.    Carbonic  Acid.  —  Black-Damp 9 

§5.    Carbonic  Oxide. —White-Damp 12 

§  6.    Sulphuretted  Hydrogen 13 

§7.    Marsh-Gas.— Fire-Damp 14 

§  8.    Expansion  of  Gases 19 

§  9.    Falling  Bodies 22 


CHAPTER  II. 

§  10.    Natural  Ventilation 23 

§  11.    Motive-Column.  —  Head  of  Air 25 

§  12.    Variation  of  Temperature,  Effects  of     ....  27 

CHAPTER  III. 

§  13.    Safety-Lamps 29 

§  14.    Comparison  of  Safety-Lamps  and  their  Efficiency         .  37 

§  14a.  Detection  of  Fire-Damp 39 

v 


IV  PREFACE. 

in  conformity  with  those  laws.  If  the  latter  is  the  ease,  they 
are  the  more  blamable ;  as  ignorance  of  the  subject,  even  at 
this  time,  may  be  excusable,  but  negligence  can  never  be. 
There  are  many  practical  hints  given  for  engineers,  who, 
owing  to  lack  of  time,  have  been  unable  to  keep  as  well 
informed  on  this  subject  as  they  may  have  wished  to  do : 
also  many  useful  memoranda,  and  tables  for  saving  time  and 
labor  when  dealing  with  questions  relating  to  ventilation, 
will  be  found  in  this  little  volume. 

The  author  would  also  state,  that  this  book  is  intended  for 
miners,  and  not  for  engineers ;  but  at  the  same  time  it  is 
believed  that  it  will  be  found  useful  to  many  engineers. 

In  hopes  of  showing  how  men's  lives  may  be  lengthened, 
and  preserved  from  the  dangers  that  lurk  in  improperly  ven- 
tilated mines,  this  work  has  been  written,  and  is  now  offered 
to  the  class  most  interested,  by  their  friend  and  well-wisher, 

E.  B.  W. 

DRIFTON,  PENN.,  "ane,  1884. 


CONTENTS. 


CHAPTER  I. 

PAGE. 

§  1.    Atmosphere. —Specific  Gravity  of  Gases  1 

§  2.    Nitrogen 5 

§  3.    Oxygen 7 

§  4.    Carbonic  Acid.  —  Black-Damp 9 

§5.    Carbonic  Oxide.— White-Damp 12 

§  6.    Sulphuretted  Hydrogen 13 

§7.    Marsh-Gas.—  Fire-Damp 14 

§  8.    Expansion  of  Gases 19 

§9.    Falling  Bodies 22 


CHAPTER  II. 

10.  Natural  Ventilation 23 

11.  Motive-Column.  —  Head  of  Air 25 

12.  Variation  of  Temperature,  Effects  of     ....  27 


CHAPTER  III. 

§  13.    Safety-Lamps 29 

§  14.    Comparison  of  Safety-Lamps  and  their  Efficiency         .  37 

§  14a.  Detection  of  Fire-Damp 39 

v 


VI  CONTENTS. 

CHAPTER  IV. 

PAGE. 

§  15.    Physical  Properties  of  Air  in  Motion         ....  40 

§  16.    Perimeter,  Area,  etc.,  denned 42 

§  17.    Friction  of  Air  in  Airways 43 

§  la    Water-Gauge 43 

§  19.    Co-efficient  of  Friction 47 

§  20.    Pressure 49 

§  21.    Pressure,  continued 50 

CHAPTER  V. 

§  22.    Laws  of  Pressure,  and  Friction  of  Air  in  Mines,  with 

Problems  illustrating  the  Same 53 

CHAPTER  VI. 

§  23.    Laws  regulating  the   Quantity  of  Air  flowing  through 

Mines 59 

§  24.    Problems  illustrating  above  Laws 61 

§  25.    Water  Gauge  and  Pressure 67 

CHAPTER  VII. 

§  26.    Ventilation  of  Single  Pits  or  Drifts 69 

§  27.    Ventilation  of  Mines  with  Two  Orifices         ...  72 

§  23.    Doors  and  Eegulators 73 

CHAPTER  VIII. 

§  29.    Splitting  the  Air 76 

§  30.    Explanation  of  Splits 77 


CONTENTS.  Vll 

PAGE. 

§  31.    Advantages  of  Splits 79 

§  32.    Area  of  Airways 85 

§  33.    Problem  on  splitting  the  Air 86 


CHAPTER  IX. 

§  34.    Quantity  of  Air  necessary  for  a  Mine     ....  88 

§  35.    Prevention  of  Explosions .92 

§  36.    Efficient  Ventilation  96 


CHAPTER  X.      . 

37.  Air  Measurements 97 

38.  Method  of  Procedure 101 

39.  Barometer    ,  103 


CHAPTER  XI. 

§  40.    History  of  Mechanical  Ventilators         ....  109 

§  41.    Fans 112 

§42.    GuibalFan 115 

§  43.    Comparative  Economy  between  Furnace  and  Fan  Venti- 
lation          .  117 

§  44.    Formulas 121 

§45.    Problems 124 

§  46.    Quantity  of  Air  necessary  per  Man         ....  128 

§  47.    Treatment  of  Asphyxiated  Persons 130 


/^::. 

fJVERSlTY 


MINE  VENTILATION. 


CHAPTER  I. 

1.  THE  atmosphere  is  composed  of  nitrogen  and 
oxygen,  with  a  trace  of  carbonic-acid  gas. 

These  three  gases,  essential  to  the  existence  of  all  ani- 
rnal  and  vegetable  life,  when  taken  separately  will  not 
support  life.  A  mechanical  mixture  of  these  gases,  in 
the  proportion  of  four  parts  of  nitrogen  to  one  part  of 
oxygen,  is  the  air  we  breathe;  which,  if  mixed  with 
deleterious  gases  (or,  as  we  say,  impure),  will  cause 
serious  physical  disorders,  and  not  unfrequently  pre- 
mature death.  Carbonic- acid  gas  rarely  exceeds  one 
part  in  sixteen  hundred  of  pure  air ;  being  present  in 
the  atmosphere,  so  say  our  best  chemists,  in  the  ratio  of 
four  parts  in  ten  thousand.  The  term  "  atmosphere  " 
designates  that  immense  expanse  or  ocean  of  gaseous 
matter  which  envelops  or  surrounds  our  earth,  com- 
monly called  uair."  It  is  supposed  that  this  atinos- 


Z  MINE   VENTILATION.  §  1 

phere  is  forty-five  miles  thick  about  the  earth :  which, 
however,  is  merely  supposition,  as  the  height  has  not 
as  yet  been  computed  with  accuracy,  although  it  has 
been  proven  that  Mariotte's  law  is  conformed  to  by 
the  gases  which  constitute  the  air ;  their  density  vary- 
ing according  to  the  pressure. 

That  the  atmosphere  varies  in  pressure  was  recog- 
nized at  an  early  period:  even  the  Florentine  pump- 
makers  were  acquainted  with  the  fact  that  water  could 
not  be  raised  by  suction  from  a  depth  of  more  than 
thirty  to  thirty-three  feet. 

Galileo  explained  this  phenomenon,  and  clearly 
demonstrated  that  the  pressure  of  the  atmosphere  was 
equal  to  the  weight  of  thirty-three  feet  of  water. 

Torricelli  argued  from  this,  that,  if  the  atmosphere 
would  support  thirty-three  feet  of  water,  it  would  not 
support  more  than  thirty  inches  of  mercury;  as  mercury 
is  about  fourteen  times  heavier  than  water.  The  result 
of  Torricelli's  investigations  and  experiments  gave  us 
the  instrument  known  as  the  barometer,  by  means  of 
which  we  can  measure  the  density  of  the  atmosphere, 
which  is  on  an  average  equal  to  the  weight  of  a  column 
of  mercury  thirty  inches  in  height  at  sea-level.  The 
temperature  of  the  atmosphere  is  not  the  same  through- 
out: it  becomes  colder  as  we  ascend;  hence  on  the  top 
of  high  mountains  we  find  snow  the  year  round. 


§  1.  MINE   VENTILATION.  3 

\ 

That  air  has  weight  may  be  shown  by  the  following 
experiment.  Take  a  vessel  whose  capacity,  say,  is  100 
cubic  inches,  exhaust  it  of  air,  and  then  weigh  it.  Let 
it  now  be  filled  with  dry  air  at  the  ordinary  tempera- 
ture and  pressure,  then  weighed  again.  Upon  second 
weighing  it  is  found  to  be  31,074  grains  heavier  than 
at  the  first.  As  the  weight  of  the  atmosphere  will 
sustain  a  column  of  mercury  whose  ba"se  is  one  inch 
square,  and  whose  height  is  thirty  inches,  it  must  press 
down  with  a  weight  equal  to  the  weight  of  the  mercury 
of  the  above  dimensions  to  balance  it.  The  weight  of 
this  mercury  is  14.7225  pounds,  and  hence  the  atmos- 
phere has  a  weight  or  pressure  equal  to  14.7  on  each 
square  inch  of  surface  exposed  to  it. 

Air  is  taken  as  the  standard  of  comparison  for  all 
gases  and  vapors.  The  chemical  composition  of  air  in 
its  natural  state  is  given  by  Dr.  Frankland  as  follows:  — 

Oxygen 20.61 

Xitrogen 77.95 

Carbonic  acid *  .        .  .04 

Moisture. 1.40 

100.00 
Dry  air  is  composed  of 

Per  cent  by  weight.        Per  cent  by  vol. 

Nitrogen 77  79 

Oxygen 23  21 

100  100 


MINE   VENTILATION. 


§1- 


The  specific  gravity  of  the  gases  in  the  following 
table  was  determined  experimentally  by  De  la  Roche 
and  Berad,  who  took  air  as  the  standard  for  gases. 


TABLE  I. 


NAME  OF  GAS. 

Symbols. 

Specific  gravity. 

AtrnospliGi'6  

N4O 

1  0000 

Hydrogen      . 

H 

0  0692 

H2O 

0.6210 

Olefiant  eras  

C9H« 

0  9672 

Carbonic  oxide      .     .     . 

CO 

09674 

N 

0.9713 

Nitric  oxide  

NO 

1.0390 

Oxygen              .          .... 

o 

1  1056 

Nitrous  oxide 

N2O 

1  5250 

Carbonic  acid    

CO.  2 

1.5290 

Sulphurous  acid     

S02 

2.470 

Manner  of  finding  the  weight  of  a  gas  compared 
with  that  of  air  is  illustrated  by  the  following  problem. 
Example.  If  1,000  cubic  feet  of  air  weigh  80.728 
pounds  when  the  temperature  is  32°  and  the  barometer 
30",  what  will  1,000  cubic  feet  of  nitrogen  weigh  under 
the  same  conditions? 

Solution.  —  From  the  table  we  find  the  density  of 
nitrogen  to  be  0.9713  when  air  is  one :  hence  we  have 
the  proportion  1  :  0.9713  =  80.728  :  Ans.,  or  78.415  + 
pounds. 


§2.  MINE   VENTILATION.  5 

2.  The  miner  lias  to  deal  with  several  gases,  espe- 
cially the  coal-miner.  It  is  therefore  imperative  that 
he  should  know  the  composition  of  these  gases,  so  as 
to  be  able  to  distinguish  them.  To  this  end,  therefore, 
a  brief  synopsis  of  some  of  the  gases  so  often  met  with 
in  mines,  together  with  their  properties,  is  here  inserted. 

Nitrogen. 
Symbol,  N.    Equivalent,  14.    Specific  gravity,  0.9713. 

The  name  signifies  nitre-maker.  It  constitutes  about 
four-fifths  of  the  atmosphere,  and  enters  into  a  great 
variety  of  combinations.  Nitrogen  is  somewhat  lighter 
than  air;  a  cubic  foot  of  the  gas  weighing  0.0784167 
pounds,  while  a  cubic  foot  of  air  weighs  0.080728 
pounds.  Nitrogen  may  be  obtained  by  burning  the 
oxygen  from  a  confined  portion  of  air.  It  is  incapable 
of  sustaining  combustion  or  animal  life :  not  that  it  has 
positive  poisonous  properties ;  but  flame  is  extinguished, 
and  animals  smother,  for  want  of  oxygen.  It  is  best 
characterized  by  its  passiveness ;  as  it  has  very  little 
affinity  or  attraction  for  other  elements,  and  upon  the 
slightest  provocation  will  free  itself  if  possible.  For 
instance,  it  may  be  induced  to  combine  with  iodine, 
and  form  "  nitric  iodide,"  a  black,  insoluble  powder, 
which  will  explode  if  moved,  jarred,  or  even  touched 
with  a  feather.  It  enters  into  the  composition  of  gun- 


6  MINE   VENTILATION.  §  2. 

powder,  nitro-gtycerine,  and  dynamite.     With  oxygen 
it  forms  five  distinct  compounds :  — 

a,  Nitrous  oxide,  N2O. 
6,  Nitric  oxide,  NO. 

c,  Nitrous  anhydride,  N2O3. 

d,  Nitrogen  peroxide,  NO2. 

e,  Nitric  anhydride,  N2O5. 

#,  Nitrous  oxide,  or  nitrogen  sub-oxide,  when  pure, 
may  be  respired  for  a  few  minutes  with  impunity.  When 
inhaled  in  large  quantities,  it  produces  a  lively  intoxi- 
cation, accompanied  with  violent  laughter:  whence  it 
derives  the  name  of  "  laughing-gas." 

5,  Nitric  oxide,  or  nitrogen  protoxide,  may  be  pre- 
pared by  treating  copper  filings,  or  turnings,  with  nitric 
acid.  The  gas  obtained  in  this  manner  is  colorless  and 
transparent :  in  contact  with  air  or  oxygen,  it  produces 
deep-red  fumes. 

e,  Nitrous  anhydride  is  an  obscure  body,  and  forms, 
with  the  elements  of  water,  an  acid  known  as  "  nitrous 
acid." 

d,  Nitrogen  peroxide  is  the  chief  constituent  of  the 
deep-red   fumes   noticed   when   nitrogen    protoxide    is 
brought  in  contact  with  air. 

e.  Nitric  anhj'dride  is  a  very  unstable,  white,  solid 
compound,    decomposing   spontaneously   into   nitrogen 
peroxide   and  oxygen.      When   treated  with  water,  it 
forms  nitric  acid. 


§  3.  MINE   VENTILATION".  7 

Oxygen. 
Symbol,  O.     Equivalent,  16,    Specific  gravity,  1.1056. 

3.  Oxygen  forms  one-fifth  part  of  the  atmosphere. 
It  is  transparent  and  colorless,  not  to  be  distinguished 
by  its  aspect  or  smell  from  atmospheric  air.  It  is  the 
most  widely  diffused  of  all  the  elements,  forming  about 
one-third  of  the  solid  crust  of  the  globe.  It  unites 
with  all  the  other  elements  to  form  compounds,  which 
are  sometimes  gaseous,  sometimes  solid,  sometimes 
liquid.  The  name  signifies  acid-former;  and,  with  one 
exception,  oxygen  enters  into  the  combination  of  acids. 
All  the  ordinary  phenomena  of  fire  and  light  which  we 
daily  witness  depend  upon  the  union  of  the  body  burned 
with  the  oxygen  of  the  air :  in  fact,  the  term  "  oxida- 
tion" may,  for  all  ordinary  purposes,  be  regarded  as 
synonymous  with  "combustion." 

Faraday  has  roughly  estimated  that  the  amount  of 
oxygen  required  daily  to  supply  the  lungs  of  the  human 
race  is  at  least  one  thousand  millions  of  pounds;  that 
required  for  the  respiration  of  the  lower  animals  is  at 
least  twice  as  much  as  this;  while  the  always  active 
process  of  decay  requires  certainly  no  less  than  four 
times  as  much.  Faraday  also  estimates  that  one  thou- 
sand millions  of  pounds  are  sufficient  to  sustain  all  the 
artificial  fires  lighted  by  man,  from  the  camp-fire  of 


8  MINE   VENTILATION.  §  3. 

the  savage  to  the  roaring  blaze  of  the  blast-furnace,  or 
the  raging  flames  of  a  grand  conflagration. 

Amount  of  Oxygen  required  Daily. 

Pounds. 

Whole  population 1,000,000,000 

Animals 2,000,000,000 

Combustion  and  fermentation 1,000,000,000 

Decay  and  other  processes 4,000,000,000 


Total  amount  of  oxygen  required  daily   .        .        .     8,000,000,000 

These  figures  are  inconceivable  ;  and,  when  we  reduce 
the  oxygen  consumed  to  tons,  we  fail  to  grasp  it,  as  it 
is  no  less  than  3,571,428  tons. 

Although  the  consumption  of  oxygen  is  so  great,  yet 
there  is  no  fear  of  its  being  exhausted ;  as,  at  the  present 
rate  of  consumption,  there  is  enough  to  last  nine  hun- 
dred thousand  years.  Oxygen  is  the  active  principle 
of  the  atmosphere.  It  devours  every  thing  with  which 
it  can  unite  :  it  corrodes  metals,  decays  fruits,  promotes 
combustion,  and  is  a  prime  necessity  for  health. 

The  body  is  a  stove,  in  which  fuel  is  burned ;  the 
chemical  action  being  the  same  as  in  any  other  stove. 
We  take  into  our  lungs  air,  and  give  out  a  poisonous 
gas,  —  carbonic-acid,  the  waste  products  of  the  com- 
bustion of  our  bodies.  From  this  we  may  learn  how 
important  a  factor  oxygen  is  for  health,  and  how  neces- 
sary it  is  that  we  have  plenty  of  fresh,  pure  air,  if  we 


§  4.  MINE   VENTILATION. 

wish  to  be  free  from  disease.  One  man  breathes  into 
his  lungs  at  each  inspiration  about  230  cubic  inches  of 
air,  or  one  gallon.  In  the  delicate  cells  of  the  lungs 
the  air  gives  up  its  oxygen  to  the  blood,  receiving,  in 
turn,  carbonic  acid  and  water,  foul  with  waste  matter 
which  the  blood  has  picked  up  in  its  circulation  through 
the  body.  Should  we  rebreathe  it  into  our  lungs,  the 
blood  will  leave  the  lungs,  not  bearing  invigorating 
oxygen,  but  refuse  matter  to  obstruct  the  whole  system. 
Without  oxygen  the  muscles  become  inactive,  the 
heart  acts  slowly,  food  is  undigested,  brain  is  clogged, 
and  at  last  such  fatal  results  as  were  manifested  in  the 
"  Black  Hole  of  Calcutta  "  implore  us  not  to  be  stingy 
or  afraid  of  "God's  blessing," — pure  air. 

4.  Having  examined  slightly  the  constituent  parts 
of  the  atmosphere,  let  us  briefly  examine  the  principal 
gases  met  with  in  coal-mining. 

Carbonic -Acid  Cras. 
Symbol,  CO2.    Equivalent,  22.    Specific  gravity,  1.53. 

One  cubic  foot  of  the  gas  at  32°  F.,  and  barometer  at 
30",  weighs  0.12845  of  a  pound. 

This  gas  is  composed  of  carbon  and  oxygen.  Miners 
have  given  it  several  names,  such  as  "  sty  the,"  "  choke- 
damp,"  "black-damp,"  and  "after-damp."  This  gas  is 


10  MINE    VENTILATION.  §4. 

always  produced  when  compounds  containing  carbon 
are  burnt  in  air  or-  oxygen.  It  may  be  produced  by 
treating  limestone  or  marble  with  hydrochloric  or 
sulphuric  acids.  The  occluded  gases  in  all  coal  con- 
tain carbonic  acid.  Carbonic  acid  is  considered  poison- 
ous, on  account  of  the  many  deaths  which  have  resulted 
from  burning  charcoal  and  carbonaceous  materials  in 
places  where  there  was  a  deficiency  of  ventilation,  and 
by  reason  of  the  fatal  nature  of  after-damp  of  explo- 
sions in  coal-mines.  Its  specific  gravity  is  1.524;  so 
that  it  is  a  little  more  than  one  and  a  half  times  as 
heavy  as  air.  It  lodges  near  the  floor  of  places  in  which 
it  is  evolved  when  little  more  than  mutual  diffusion  is 
going  on.  Owing  to  its  great  density,  it  may  be  poured 
from  one  vessel  to  another.  It  is  the  only  gas,  except 
nitrogen,  which  is  evolved  by  most  bituminous  coals ; 
and,  when  it  is  given  off  in  quantity,  active  ventilation 
is  required  to  carry  it  off. 

Le  Blanc,  and  many  other  chemists,  affirm  that  air  con- 
taining more  than  five  parts  in  a  thousand  is  injurious 
to  breathe.  Mr.  J.  W.  Thomas  of  England,  while  not 
asserting  that  it  is  not  injurious,  says,  that  "in  levels 
and  seams  of  semi-bituminous  and  bituminous  coals  in 
South  Wales,  in  part  or  wholly  worked  to  the  dip,  with 
scanty  ventilation  in  some  particular  spots,  through  the 
non-completion  of  air-splits,  or  conveyances,  men  often 


§4.  MINE  VENTILATION. 

work  in  an  atmosphere  containing  from  two  to  five  per 
cent  of  this  gas  for  hours."  Be  that  as  it  may,  the  sys- 
tem, uninspired  by  the  energizing  oxygen,  is  sensitive 
to  cold.  The  pale  cheek,  the  lustreless  eye,  the  languid 
step,  shortness  of  breath,  speak  but  too  plainly  of  oxygen 
starvation.  "In  such  a  soil,  catarrh,  scrofula,  miners' 
asthma,  and  consumption  run  riot." 

Miners  call  the  carbonic  acid  produced"  by  the  explo- 
sion of  fire-damp,  "after-damp."  They  fear  it  almost 
as  much  as  fire-damp,  as  it  instantly  destroys  the  lives 
of  all  who  may  have  escaped  the  flames  of  the  explo- 
sion. This  property  of  carbonic  acid,  of  choking  or 
smothering,  has  of  late  years  been  made  use  of  for 
putting  out  fires  in  coal-mines.  In  one  case,  an  Eng- 
lish mine  which  had  been  burning  twenty  years  was 
smothered  by  pouring  into  it  eight  billion  cubic  feet  of 
carbonic  acid,  and  then  closing  it  up  for  one  month. 
At  the  end  of  the  month  the  mine  was  opened,  and 
found  to  be  ready  for  the  resumption  of  labor. 

When  found  alone  in  a  mine,  carbonic  acid  is  not 
considered  as  dangerous  as  fire-damp,  since  it  will  not 
burn.  Carbonic  acid,  at  the  ordinary  temperature  and 
pressure,  is  a  gas.  It  solidifies  when  subjected  to  great 
pressure ;  but,  as  soon  as  the  pressure  is  removed,  it 
returns  to  the  gaseous  state :  therefore  the  term  "  car- 
bonic acid  "  is  applied  as  well  to  the  gas  as  to  the  acid. 


12  MINE  VENTILATION.  §5. 

Carbonic  Oxide. 
Symbol,  CO.     Equivalent,  14.    Specific  gravity,  0.9674. 

5.  One  cubic  foot  of  the  gas  at  32°  F.,  and  barometer 
of  30",  weighs  0.078305  of  a  pound. 

This  gas  is  sometimes  called  "white-damp."  From 
experiments  made  by  Dr.  Meyer  and  J.  W.  Thomas,  it 
was  found,  that,  during  every  explosion,  large  quanti- 
ties of  this  gas  were  formed,  and  that  the  fatal  effects 
of  the  after-damp  are  in  a  great  measure  due  to  its 
presence.  Carbonic  oxide  is  an  odorless  and  colorless 
gas,  incapable  of  supporting  the  combustion  of  other 
bodies,  but  is  itself  an  inflammable  gas.  It  possesses 
very  poisonous  properties,  which  act  powerfully  on  the 
blood  and  nervous  system,  producing,  when  inhaled  in 
very  small  quantities,  a  most  unpleasant  sensation,  fol- 
lowed quickly  by  headache,  and  disinclination  to  move, 
prostration  and  inactivity :  if  continued  to  be  breathed, 
asphyxia  follows,  and  death  soon  results.  Air  contain- 
ing only  one-half  per  cent  of  this  gas  would  prove  fatal, 
if  inspired  for  any  length  of  time.  Mr.  Thomas  advo- 
cates oxygen  and  induced  artificial  breathing,  for  those 
who  are  overcome  by  this  gas,  in  preference  to  the 
administration  of  alcoholic  stimulants. 


§  6.  MINE  VENTILATION.  13 

The  composition  of  carbonic  oxide  is, 

By  weight.      By  volume. 

Carbon 42.86  1 

Oxygen 57.14  1 

100.00  2 

This  gas  is  narcotic,  and,  when  breathed  in  a  concen- 
trated form,  would  produce  no  pain,  the  body  passing 
instantly  into  a  state  of  coma.  Whatever  position  the 
victim  assumed,  in  that  position  he  would  be  found 
dead,  unless  moved  by  some  other  means.  u  Carbonic 
acid,  and  the  nitrogen  left  after  an  explosion,  would 
be  fatal  in  their  effects ;  but  very  often  men  have  suc- 
cumbed to  supposed  after-damp,  while  their  lamps 
burned  well.  The  presence  of  carbonic  acid  and  nitro- 
gen will  not  account  for  the  result  or  phenomena." 

SULPHUKETTED    HYDROGEN. 

Symbol,  SH2.     Equivalent,  17.     Specific  gravity,  1.178. 

6.  One  cubic  foot  of  the  gas  at  32°  F.  and  barometer 
of  30",  weighs  0.09492  of  a  pound. 

This  gas,  although  not  common,  is  met  with  some- 
times in  mines.  It  is  colorless,  but -easily  distinguished 
by  its  peculiar  smell,  —  that  of  rotten  eggs.  It  may 
be  prepared  by  treating  sulphide  of  iron  with  dilute 
sulphuric  acid.  The  composition  of  sulphuretted  hydro- 
gen is, 


14                                     MINE   VENTILATION.  §  7 

By  weight.  By  atcras. 

Sulphur 94.12  1 

Hydrogen 5.88  2 


100.00  3 

When  mixed  with  oxygen,  it  will  explode  if  ignited. 
When  inhaled  in  a  pure  state,  it  is  a  powerful  narcotic 
poison,  and  produces  fainting  and  asphyxia  when  pres- 
ent in  very  small  proportions  of  the  atmosphere.  It 
appears  to  be  probable  that  the  gas  is  generated  in 
small  quantities  in  old  worked-out  mines.  Some  claim 
that  it  is  formed  by  the  decomposition  of  pyrites  in  old 
workings ;  others,  that  it  is  not  formed  in  this  manner, 
but  by  the  decomposition  of  props  and  timber  standing 
in  water,  by  breaking  up  the  sulphate  of  lime,  and 
assimilating  its  oxygen,  while  sulphur  seizes  upon  the 
Imlrogen  of  the  wood  to  form  sulphuretted  hydrogen. 
This  gas  is  also  known  as  hydrosulphuric  and  sulphuric 
acid  gas. 

MARSH-GAS. 
Symbol,  CH4.     Equivalent,  8.     Specific  gravity,  0.55314. 

7.  One  cubic  foot  of  this  gas,  at  32°  F.  and  barome- 
ter of  30",  weighs  0.044665  of  a  pound. 

It  is  known  by  several  names, — proto-carburetted  hy- 
drogen, light  carburetted  hydrogen,  hydride  of  methyl, 
fire-damp.  Marsh-gas,  however,  is  better  known  to 


§  7.  MINE   VENTILATION.  15 

miners  as  "  fire-damp/'  It  is  colorless,  tasteless,  odor- 
less, when  pure,  burning  with  a  yellowish  flame.  It  is 
formed  in  swamps  and  marshy  places  by  the  decom- 
position of  vegetable  matter,  and  may  be  seen  bubbling 
up  through  the  water  when  the  mud  is  stirred  beneath. 
Marsh-gas  is  found  in  such  quantities  in  some  places, 
that  it  is  used  for  lighting  towns,  and.  evaporating 
brine.  In  the  oil-regions  it  frequently  bufsts  forth  with 
explosive  violence,  throwing  the  oil  high  in  the  air  when 
the  drill  nears  it.  Coal-gas  contains  about  thirty-eight 
per  cent  of  marsh-gas.  When  marsh-gas  is  evolved 
in  the  shape  of  "  blowers,"  it  constitutes  about  ninety- 
six  per  cent  of  the  total  volume.  Blowers  sometimes 
assume  enormous  dimensions,  and  have  been  conveyed 
from  the  workings  to  the  surface  by  means  of  pipes, 
and  utilized.  Marsh-gas  is  not  poisonous.  Sir  H.  Davy, 
of  safety-lamp  fame,  was  the  first  to  experiment  on  this 
gas.  He  found,  that,  when  mixed  with  three  and  a  half 
times  its  volume  of  air,  it  did  not  explode ;  with  five 
and  a  half  times  its  volume,  it  exploded  slightly ;  and, 
when  mixed  with  eight  or  nine  volumes  of  air,  the  force 
of  explosion  was  greatest.  When  there  is  a  deficiency 
of  ventilation,  the  fire-damp  is  said  to  rise  to  the  upper 
portion  or  top  of  a  gallery,  and  there  remain,  because 
of  its  being  lighter  than  air.  It  is  also  said  that  car- 
bonic acid,  being  heavier  than  air,  lodges  on  the  "floor" 


16  MINE   VENTILATION.  §  7 

or  "  thill "  of  a  mine.  Mr.  Thomas,  in  his  book  on 
"Mines,  Gases,  and  Ventilation,"  says,  "This  impres- 
sion is  erroneous;  and  while  not  denying  that  fire-damp 
is  often  found  in  larger  quantities  near  the  roof,  and 
carbonic  acid  in  larger  quantities  near  the  floor,  these 
positions  do  not  prove  that  they  have  lodged  there,  nor 
is  it  so :  on  the  contrary,  marsh-gas  is  always  diffusing 
in  every  direction  ;  and  it  is  only  in  those  places  where 
the  gas  is  evolved  in  greater  quantity  than  will  diffuse, 
or  become  carried  away  by  the  ventilation,  that  accu- 
mulation takes  place.  These  erroneous  ideas  in  refer- 
ence to  marsh-gas  arose  from  the  fact  that  it  is  found 
in  the  crevices  and  holes,  and  near  the  roof,  of  coal- 
mines." The  explanation  of  this  is  very  simple.  The 
fact  of  portions  of  top-rock  falling,  and  the  squeezing-in 
or  lowering  of  the  top  throughout  the  whole  worked 
portion  above  the  coal,  affords  communication  with,  it 
may  be,  some  rider  or  un  worked  seam  of  coal  above, 
with  the  receding  working-face,  or  with  crevices  which 
are  in  communication  with  stores  of  fire-damp  extend- 
ing to  considerable  distances.  Now,  the  pressure  of 
the  atmosphere  being  the  same  on  all  sides,  the  gas  in 
the  fissures  and  cracks  in  the  top  are  subjected  to  that 
pressure  externally,  so  that  air  finds  no  outlet  through 
these  cracks,  and  the  diffusion  which  takes  place  is 
simply  "  natural "  or  mutual  diffusion. 


§  7.  MINE   VENTILATION.  17 

The  fire-damp  issuing  into  these  cracks,  etc.,  encoun- 
ters the  same  pressure  as  if  issuing  direct  into  the  air- 
current;  so  that  it  would  find  its  way  downwards  by 
virtue  of  the  extra  force  of  pressure  of  the  imprisoned 
gas  into  the  top  of  the  holes,  goaves,  or  receptacles  in 
the  top-rock,  and  it  would  be  more  likely  to  escape  or 
find  an  exit  in  these  places,  or  come  in  contact  with  the 
ventilating  current  here,  owing  to  the  fact  that  more 
easy  communication  is  afforded  by  the  dislocation  and 
partial  disintegration  of  the  top  caused  by  a  fall, 
followed  by  a  partial  .opening-up  of  the  surrounding 
mass.  The  fire-damp,  therefore,  instead  of  accumulating 
and  lodging  at  the  roof  of  the  gallery  by  virtue  of  its 
lesser  density,  is  forced  downwards  until  it  finds  its  way 
into  the  holes  and  other  receptacles,  and  is  continually 
fed  from  above. 

"When  marsh-gas  escapes  from  the  floor,  and  makes 
its  appearance  in  quantity  near  the  roof,  it  shows 
deficiency  of  ventilation,  or  a  strong  outpour  of  gas; 
but  even  then,  if  there  is  any  ventilation  at  all,  it  will 
be  largely  mixed  with  air." 

The  reason  that  fire-damp  is  in  the  form  of  an  explo- 
sive mixture  in  holes  in  the  top,  is  because  it  is  fed 
more  quickly  from  above  than  it  is  able  to  diffuse ;  the 
ventilating  current  not  affecting  it  to  a  very  great 
extent. 


18  MINE   VENTILATION.  §  7. 

Let  the  lines  below  represent  a  gallery  from  which 
some  of  the  top  has  fallen.  F  is  the  floor,  RR  the  roof, 
and  H  the  hole  caused  by  the  fall.  If  a  lamp  be  raised 
about  halfway  between  R  and  F,  an  explosive  mixture 
may  be  encountered ;  but,  if  the  lamp  is  held  near  the 


cracks  in  RR,  not  a  trace  of  gas  will  be  indicated  by  it, 
provided  there  is  sufficient  ventilation.  Gradually  stop 
the  ventilating  current,  so  that  the  air  scarcely  travels, 
and  then  apply  the  lamp,  and  the  fire-damp  issuing  from 
the  cracks  may  be  detected.  Active  ventilation  sweeps 
away  all  the  gas  which  escapes  from  cracks  in  the  line 
of  the  top  rock  or  roof;  but  as  the  current  can  find  no 
outlet  through  the  hole  at  H,  and  encounters  a  press- 
ure equal  or  superior  to  that  along  the  roof,  it  travels 
onward,  heedless  of  any  gas  situated  out  of  the  line 
RR.  When  fire-damp  accumulates  near  the  roof  or 
top  line  of  a  gallery  or  heading,  it  indicates  that  the 
gas  is  given  off  in  greater  quantity  than  can  be  carried 
off  by  the  ventilation ;  and,  where  any  such  accumula- 
tion takes  place,  there  must  be  either  a  deficiency  of 
ventilation,  or  an  unusual  inpour  of  gas. 


§8.  MINE  VENTILATION..  19 

EXPANSION  OF  GASES. 

8.  One  of  the  chief  characteristics  of  any  gas  is  its 
expansive  property.  To  calculate  the  expansion  of  any 
volume  of  air,  the  starting-point  must  always  be  taken 
at  0°  on  Fahrenheit's  scale ;  for  air  at  that  temperature 
will  expand  ?-J-9  of  its  volume  for  every  degree  of  heat 
added.  Therefore  459  cubic  feet  of  air  at  0°  will  be- 
come 460  cubic  feet  at  1°  F. 

Careful  experiments  show  that  459  cubic  feet  of  air 
at  0°  F.  weigh  39.76  pounds,  when  the  pressure  is  30 
inches  of  mercury  of  the  density  due  to  32°,  —  a  press- 
ure equal  to  14.7  pounds  per  square  inch ;  but,  when 
the  pressure  is  one  inch,  it  weighs  only  ^  part  of  this, 
or  1.3253  pounds.  To  find  the  weight  of  a  cubic  foot 
of  air  at  any  temperature  or  height  of  the  barometer,  let 

B  =  height  of  the  barometer  in  inches, 
t  =  temperature  by  Fahrenheit's  thermometer ; 

then 

1.3253  X  B 


(1) 


459  +  t 


Problem.  —  What  is  the  weight  of  a  cubic  foot  of  air, 
the  temperature  of  which  is  96°,  under  a  barometric 
pressure  of  29.5  inches  of  mercury? 

By  substituting  29.5  in  formula  1  for  B,  and  96°  for 


20  .MINE   VENTILATION.  §8. 

f,  and  then  performing  the   operations  indicated,  we 
have 

1.3253  x  29.5       A  „, 

W  = =  0.07044  pound 

459  +  96 

as  the  weight  of  a  cubic  foot  of  air  under  the  above 
conditions. 

The  following  table  has  been  made  out  to  facilitate 
calculations.  It  gives  the  weight  of  100  cubic  feet  of 
air  in  pounds  at  different  barometrical  pressures. 


§8. 


MINE  VENTILATION. 
TABLE  II. 


21 


III 

0     d     % 

to 

II, 

to 

«      2 

.2    " 

1115.' 

aT 

1  *  ® 

o  .S  8 

g  .S  8 

O.S8 

g  .2  53 

^   °-  a  of 

-.-j  •£ 
2  ^3 

o^   1 

*** 

®  «M 

*s  *•£ 

•s2  J 

•S  *~   v  "S 
|g|| 

8,-g 

1  1 

111 

§  «  § 

tj)  ••:*    fl> 

.SP  «  * 

111 

|l|l 

^    «M    -0 

£*•« 

^•o 

^£-0 

^  «t-.  "O 

g    0  T3    0 

30 

7.857 

7.993 

8.129 

8.265 

8.400 

0.136 

32 

7.826 

7.961 

8.096 

8.231 

8.366 

0.135 

42 

7.670 

7.802 

7.934 

8.066 

8.198 

0.132 

52 

7.519 

7.649 

7.779 

7.909 

8.039 

0.130 

62 

7.375 

7.502 

7.629 

7.756 

7.883 

0.127 

72 

7.236 

7.361 

7.486 

7.611 

7.736 

0.125 

82 

7.103 

7.225 

7.347 

7.471 

7.593 

0.122 

92 

6.974 

7.094 

7.214 

7.334 

7.454 

0.120 

102 

6.849 

6.968 

7.085 

7.204 

7.323 

0.119 

112 

6.729 

6.845 

6.961 

7.077 

7.193 

0.116 

122 

6.614 

6.728 

6.842 

6.956 

7.070 

0.114 

132 

6.502 

6.614 

6.726 

6.838 

6.950 

0.112 

142 

6.394 

6.504 

6.614 

6.728 

6.834 

0.110 

152 

6.289 

6.397 

6.506 

6.614 

6.722 

0.108 

162 

6.188 

6.294 

6.401 

6.508 

6.614 

0.106 

172 

6.089 

6.-195 

6.300 

6.405 

6.509 

0.104 

182 

5.995 

6.098 

6.201 

6.304 

6.408 

0.103 

192 

5.903 

6.004 

6.106 

6.208 

6.309 

0.101 

202 

5.813 

5.913 

6.014 

6.114 

6.214 

0.100 

212 

5.726 

5.825 

5.924 

6.023 

6.122 

0.099 

222 

5.642 

5.739 

5.837 

5.934 

6.032 

0.097 

232 

5.561 

5.657 

5.753 

5.843 

5.939 

0.096 

242 

5.481 

5.576 

5.671 

5.765 

5.861 

0.095 

252 

5.404 

5.497 

5.591 

5.684 

5.777 

0.093 

262 

5.329 

5.421 

5.513 

5.605 

5.697 

0.092 

272 

5.256 

5.347 

5.438 

5.527 

5.618 

0.091 

282 

5.185 

5.275 

5.364 

5.453 

5.542 

0.089 

292 

5.117 

5.205 

5.293 

5.381 

5.469 

0.088 

302 

5.049 

5.136 

5.223 

5.310 

5.397 

0.087 

22  MINE   VENTILATION.  §9. 

9.  As  we  have  seen,  air  has  weight,  and  therefore 
becomes  subject  to  the  "  physical  laws  "  that  govern 
liquids  and  falling  bodies;  i.e.,  air  is  acted  on  by  gravity 
in  the  same  manner  as  a  solid. 

Let  li  =  the  distance  fallen  through  in  feet. 

v  =  the  velocity  acquired  at  the  end  of  the  fall,  in 

feet  per  second. 
g  =  the  distance  in  feet  which  an  unresisted  gravitat- 

ing body  falls   in   the  first  second  of   time  ; 

which  distance  has  been  found  by  experiment 

to  be  16T\  feet  near  the  earth's  surface. 

Since  a  body  falls  16.08'  in  one  second,  it  gains  a 
velocity  of  32.16'  at  the  end  of  the  first  second:  hence 
we  have 


(2)  v  =  V/V*  =  8.0208  \fh. 

In  this  equation  h  represents  the  he.cessary  height,  in 
feet,  of  a  vertical  air-column  which  will  produce  by  its 
weight  a  velocity  equal  to  v.  If  this  velocity  be  repre- 
sented in  feet  per  minute,  we  shall  have 

(3)  v  =  8.020SV^  X  60  =  481.2^, 

and 

tf  _v*_ 

~  (481.  2)2~  231,600' 


§10. 


MINE   VENTILATION. 


23 


These  formulae  (2),  (3),  and  (4)  are  only  theoreti- 
cally true  as  regards  air  in  mines,  the  pressure  or  head 
of  air-column  required  being  from  ten  to  twenty  times 
as  much  in  order  to  overcome  the  friction  and  resist- 
ance of  airways,  etc.,  in  underground  workings ;  and, 
were  it  not  for  these  resistances,  very  small  pressure 
would  suffice  to  produce  great  velocity. 


CHAPTER  II. 

NATURAL  VENTILATION. 

10.   MOTION  in  air  is  caused  by  pressure,  or  differ- 
ence of  pressure.    When  air  becomes  heated,  it  ascends, 
because  it  assumes  a  larger  volume ; 
and,  as  the  same  volume  of  cold  air 
is  heavier,   it  pushes   the   warmer  A 
up,  or  out  of  its  place.     This  phe- 
nomenon in  the  open  air  gives  rise 
to  winds  and  breezes,  which  vary 
in  intensit}',  according  as  the  cool 
air  takes  the  place  of  the  warm  air,  rapidly  or  slowly. 

Suppose  we  have  two  shafts  (connected,  as  in  the 
above  figure)  of  equal  depths,  the  air  in  them  having 


24  MINE   VENTILATION.  §10. 

the  same  temperature  and  density  throughout.  If  no 
artificial  means  be  used  to  cause  a  movement  in  either 
direction,  —  down  one,  and  up  the  other,  —  the  air  will 
be  in  equilibrium,  and  be  stagnant.  If  the  tops  of  the 
shafts  be  not  of  the  same  height,  as  AB,  the  air  AE,  if 
of  the  same  density  and  temperature,  would  have  the 
same  effect  as  if  the  shaft  rose  to  E,  and  remain  in 
equilibrium.  Suppose,  now,  that  the  external  air  is  of 
lower  temperature  than  the  air  in  the  shafts,  and  the 
column  AB  lower  in  temperature  than  CD,  a  movement 
of  the  air  then  takes  place  from  A  towards  C.  On  the 
contrary,  if  the  external  air  be  warmer  than  that  of 
the  shafts,  the  shaft  AB  will  be  the  upcast,  and  circu- 
lation will  be  from  0  to  A>  on  account  of  the  heavier 
column  of  air  CD. 

This  is  the  principle  upon  which  furnaces  are  em- 
ployed to  ventilate  mines.  They  are  placed  at  the 
bottom,  or  near  the  bottom,  of  the  upcast  shaft.  The 
heat  given  off  by  them  raises  the  temperature  of  the  air, 
which  expands  ?-J-g  part  of  its  volume  for  each  degree 
of  heat  added,  and  hence  becomes  lighter.  The  cooler 
air  of  the  downcast  shaft  is  now  able,  owing  to  its 
greater  density,  to  fall  down  the  shaft,  and  push  the 
air  of  the  mine  into  the  upcast,  which  becomes,  in  turn, 
heated  by  the  furnace.  Let  us  take  an  example  to  see 
in  what  manner  this  difference  in  density  will  cause 


§  11.  MINE   VENTILATION.  25 

ventilation.  Suppose  the  two  shafts  to  be  of  equal 
depth,  say  900  feet,  and  suppose  the  barometer  to  stand 
at  29  inches ;  also  let  the  temperature  in  the  downcast 
be  assumed  to  be  42°,  and  that  of  the  upcast  72°. 
From  the  table  on  p.  21,  we  find  that  100  cubic  feet  of 
air  at  42°  weigh  7.67  pounds :  therefore  900  cubic  feet 
weigh  9  times  as  much,  or  69.030  pounds.  Again :  we 
find  100  cubic  feet  of  air  at  72°  weigh  7.236  pounds, 
and  hence  900  cubic  feet  weigh  65.124  pounds.  The 
difference  between  these  weights  will  give  the  pressure 
that  would  cause  circulation. 

Pounds. 

900  cubic  feet  at  42°  =  69.030 
900  cubic  feet  at  72°  -  65.124 

Difference  in  weight  3.906 

This  pressure  in  the  open  air  would  produce  a  velocity 
of  wind  between  twenty-five  and  thirty  miles  per  hour. 

11.  The  "  motive-column"  is  a  "head  of  air"  of  such 
a  height  that  it  will  equal  the  difference  between  the 
weight  of  the  downcast  and  upcast  columns  of  air. 

Let  M  =  the  motive-column,  or  head  of  air, 
D  =  the  depth  of  the  upcast  in  feet, 
t    —  the  temperature  of  the  upcast  in  degrees, 
ll   =  the  temperature  of  the  downcast  in  degrees, 


28  MINE   VENTILATION.  §11. 

then, 

M  ^  D  X  459*  +  ^ 

Problem.  —  Find  the  motive-column  which  would  pro- 
duce a  pressure  of  3.906  pounds  when  the  upcast  has 
a  depth  of  900  feet  and  a  temperature  of  72°^  and  the 
downcast  has  the  same  deptli  and  a  temperature  of  42°. 

Substituting  in  formula  5  we  have 


as  the  length  of  the  motive-column. 

The  height  of  a  column  of  this  air,  one  foot  in  area, 
weighing  one  pound,  may  be  found  by  dividing  the 
motive-column  by  the  pressure  per  square  foot;  thus:  — 

53.8922 
"3790 6"  : 

The  relative  diameters  of  the  shafts  make  no  differ- 
ence upon  the  total  pressure,  so  far  as  the  considera- 
tions regarding  ventilation  are  concerned.  This  is 
termed  "  the  pneumatic  paradox  ;  "  for  if  we  have  one 
square  foot  area  for  a  downcast,  and  an  upcast  of  ten 
square  feet,  the  pressure  on  each  square  foot  of  upcast 
will  be  the  same  as  on  the  one  square  foot  of  the  down- 
cast, provided  there  is  no  friction. 


§  12.  MINE   VENTILATION.  27 

When  calculating  the  weight  of  the  motive-column, 
we  must  bear  in  mind  that  it  is  not  the  total  amount 
of  air,  or  the  total  number  of  cubic  feet,  that  we  seek, 
but  the  length  of  an  air-column  which  has  for  its  base 
one  square  foot,  and  which  weighs  a  certain  amount 
for  each  cubic  foot  in  height. 

12.  The  temperature  of  the  atmosphere  varies  at 
different  seasons  of  the  vear.  This  variation  causes 
considerable  increase  and  decrease  in  the  ventilation 
of  mines.  To  illustrate  this,  suppose  we  have  a  mine 
900  feet  deep,  what  will  be  the  ventilating  pressure, 
when  the  temperature  in  the  downcast  is,  on  an  aver- 
age, 42°,  and  in  the  upcast  202°,  the  barometer  being 
30"  on  an  average  in  the  two  shafts,  which  are  equal 
in  length? 

Pounds. 

900  cubic  feet  of  air  at   42°  F.  =  71.406 
900  cubic  feet  of  air  at  202°  F.  =  54.126 

Difference  in  weigbt      .     .     .17.280 

Suppose,  now,  the  temperature  of  the  downcast  to 
be  raised  to  82°  F.,  then 

Pounds. 

900  cubic  feet  of  air  at    82°  F.  =  66.123 
900  cubic  feet  of  air  at  202°  F.  =  54.126 


Difference  in  weight .    .    .    .11.997 


28  MINE   VENTILATION.  §12 

17.280  —  11.997  —  5.283  pounds  of  the  total  pressure 
lost  by  this  change  of  temperature.  As  the  tempera- 
ture does  not  change  so  much  as  40°,  in  a  short  time  it 
will  not  have  so  marked  an  effect  upon  the  ventilation 
of  mines :  still,  an  increase  of  power  will  be  required 
during  the  summer  months  in  order  to  keep  the  venti- 
lation uniform  during  the  year. 

From  the  above,  it  may  be  seen  that  natural  ventila- 
tion may  be  more  during  the  winter  than  during  the 
summer  months.  Where  furnaces  or  steam-jets  are 
employed  to  produce  ventilation,  the  longer  the  upcast, 
the  better;  as  the  longer  upright  column  of  light  air 
gives  rise  to  a  brisker  ventilation.  For  this  reason, 
furnaces  should  not  be  used  in  shallow  pits. 

When  coal  is  worked  at  a  dip,  the  effect  of  natural 
ventilation  is  very  complicated ;  and  in  many  instances 
there  will  be  little  benefit  derived  therefrom  at  any 
season  of  the  year,  owing  to  the  tendency  of  the  heated 
air  to  ascend  against  the  down  current.  Natural  venti- 
lation is  not  a  help  to  artificial  ventilation,  but  often  is 
of  very  great  hinderance  to  a  fan,  on  account  of  the 
vacillating  atmospheric  changes.  On  this  account, 
therefore,  the  inlet  and  outlet  should  be  as  nearly  as 
practicable  on  the  same  level.  High  winds,  directed  by 
hills,  blowing  against  the  exhaust  duct  of  a  fan,  greatly 
impede  its  action. 


§13. 


MINE   VENTILATION. 


29 


TABLE   III. 

VELOCITY  AND  POWER  OF  WINDS     (SMEATON). 


Velocity. 
Miles  per  hour. 

Perpendicular  force  on 
one    square    foot,    in 
pounds  avoirdupois. 

Common  appellation  of  such 
winds. 

1 

.005 

Hardly  perceptible. 

4 

5 

.079) 
.123  J 

Gentle  wind. 

10 
15 

.492  / 
1.107  f 

Pleasant  breeze. 

20 
25 

1.968  1 
3.075  ] 

Very  brisk. 

30 
35 

4.429  ) 
6.027  f 

High  wind. 

40 

7.873 

Very  high. 

50 

12.300 

Storm. 

60 

17.715 

Great  storm. 

80 

3K490 

Hurricane. 

100 

49.200 

Violent  hurricane. 

CHAPTER    III. 

SAFETY-LAMPS. 

13.  IN  the  year  1814  Mr.  Buddie,  an  Englishman, 
read  a  paper  before  a  society  formed  for  preventing 
accidents  in  coal-mines,  illustrating  the  various  modes 
employed  in  the  ventilation  of  collieries  by  plans  and 
sections. 

At  that  time  the  only  light  used  in  coal-mines  was 


30  MINE   VENTILATION.  §13. 

the  candle  made  of  sheep  or  ox  tallow,  the  latter  being 
considered  the  better. 

When  the  air  in  the  mine  became  mixed  with  inflam- 
mable gas,  the  mode  of  determining  its  existence  and 
degree  of  inflammability  was  described  by  Mr.  Buddie 
as  follows :  — 

"  In  the  first  place  the  candle,  called  by  the  colliers 
'the  low,'  is  trimmed;  that  is,  the  liquid  fat  is  wiped 
off,  the  wick  snuffed  short,  and  carefully  cleansed  of  red 
cinders,  so  that  the  flame  may  burn  as  purely  as  possi- 
ble. The  candle,  being  thus  prepared,  is  holden  be- 
tween the  fingers  and  thumb  of  the  one  hand ;  and  the 
palm  of  the  other  hand  is  placed  between  the  e}re  of 
the  observer  and  the  flame,  so  that  nothing  but  the 
spire  of  the  flame  can  be  seen,  as  it  gradually  towers 
over  the  upper  margin  of  the  hand.  The  observation 
is  generally  commenced  near  the  floor  of  the  mine,  and 
the  light  and  hand  are  gently  raised  upwards  till  the 
true  state  of  the  circulating  current  is  ascertained. 
The  first  indication  of  the  presence  of  inflammable  air 
is  a  slight  tinge  of  blue,  a  bluish-gray  color,  shooting 
up  from  the  top  of  the  spire  of  the  candle,  and  termi- 
nating in  a  fine  extended  point.  This  spire  increases 
in  size,  and  receives  a  deeper  tinge  of  blue,  as  it  rises, 
through  an  increased  proportion  of  inflammable  gas, 
till  it  reaches  the  firing-point.  The  experienced  collier 


§13.  MINE  VENTILATION.  31 

knows  all  the  gradations  of  shew  (as  it  is  called),  and 
seldom  fires  the  inflammable  gas,  except  in  cases  of 
sudden  discharge." 

When  the  air  was  highly  charged  with  inflammable 
gas,  the  steel  mill  was  resorted  to.  It  consisted  of  a 
steel  wheel,  to  which  was  applied  a  piece  of  flint  when 
it  was  turned  rapidly,  thus  throwing  off  a  continuous 
succession  of  sparks,  the  light  of  whioh  was  rather 
uncertain:  however,  it  was  a  substitute.  But  as  it  re- 
quired one  man  to  work  the  mill  for  every  man  cutting 
coal,  mining  became  too  expensive ;  and  only  those  por- 
tions of  the  mine  were  worked  where  a  sufficient  cur- 
rent of  air  could  be  brought  to  bear  upon  the  gas  to 
dilute  it  sufficiently  to  allow  of  candles  being  used. 

In  1814  Dr.  Clanny  produced  a  lamp  by  which  a 
light  could  be  used  in  an  inflammable  mixture  of  gas 
with  impunity.  The  insulation  of  the  flame  was  accom- 
plished by  means  of  water  ;  and,  although  the  first  lamp 
which  was  produced,  it  was  too  complicated  and  cum- 
brous for  general  use. 

In  1815  —  at  the  same  time,  but  in  distant  localities 
• — Mr.  George  Stephenson  and  Sir  Humphry  Davy  both 
produced  lamps  which  insulated  lights  in  inflammable 
mixtures  of  fire-damp  without  exploding  the  gas  exter- 
nally. These  productions  have  been  of  the  utmost 
importance  in  coal-mining,  and  consequently  to  the 
commercial  interests  of  the  country  generally. 


32  MINE   VENTILATION.  §13. 

Mr.  Stephenson  reasoned,  that  "if  a  lamp  could  be 
made  to  contain  the  burnt  air  above  the  flame,  and  to 
permit  the  fire-damp  to  come  in  below  in  a  small  quan- 
tity, to  be  burned  as  it  came  in,  the  burnt  air  would 
prevent  the  passing  of  the  explosion  upwards ;  and  the 
velocity  of  the  current  of  the  air  from  below  would 
also  prevent  it  passing  downwards."  He  accordingly 
constructed  a  lamp  of  tin,  with  a  hole  in  the  bottom  to 
admit  the  air  to  the  flame,  and  a  top  perforated  with 
holes.  By  experiments  with  this  lamp  he  discovered 
the  true  principles  of  the  safety-lamp. 

Sir  H.  Davy,  at  about  the  same  time,  communicated 
with  a  friend  that  he  had  "discovered  that  explosive 
mixtures  of  mine-damp  will  not  pass  through  small 
apertures  or  tubes,  and  that  if  a  lamp  or  lantern  be 
made  air-tight  on  the  sides,  and  furnished  with  aper- 
tures to  admit  the  air,  it  will  not  communicate  flame 
to  the  outward  atmosphere."  He  subsequently  found 
that  "iron-wire  gauze,  composed  of  wires  from  one- 
fortieth  to  one-sixtieth  of  an  inch  in  diameter,  and 
containing  twenty-eight  wires,  or  seven  hundred  and 
eighty-four  apertures  to  the  inch,  was  safe  under  all 
circumstances." 

The  process  by  which  Mr.  Davy  arrived  at  the  above 
conclusion  is  given  by  himself  in  a  small  work  "  On 
the  Safety-Lamp  for  Coal-Mines,  with  some  Researches 


§  13.  MINE  VENTILATION.  33 

on  Flame : "  "  In  reasoning  upon  the  various  phenom- 
ena brought  about  by  my  various  experiments,  it  oc- 
curred to  me,  —  as  considerable  heat  was  required  for 
the  inflammation  of  the  fire-damp,  and  as  it  produced,  in 
burning,  a  comparatively  small  degree  of  heat,  —  that 
the  effect  of  carbonic  acid  or  azote,  and  of  the  sur- 
faces of  the  small  tubes  in  preventing  its  explosion, 
depends  upon  their  cooling  powers,  or  their  lowering 
the  temperature  of  the  exploding-mixture  so  much  that, 
it  was  no  longer  sufficient  for  its  continuous  inflamma- 
tion." 

Mr.  Stephenson's  lamp  has  been  much  improved.  It 
consists  of  a  glass  cylinder  above  the  lamp,  covered  by 
a  cylinder  of  wire  gauze ;  and,  instead  of  air  passing 
through  the  perforated  plate,  it  passes  through  the 
meshes  of  the  gauze  (Fig.  1). 

The  Davy  lamp  differs  from  the  Stephenson,  inasmuch 
as  the  former  admits  air  through  the  meshes  of  the 
wire  on  all  sides :  consequently,  when  immersed  in  an 
inflammable  mixture,  the  whole  cylinder  becomes  filled 
with  flame,  and  ultimately  the  wires  become  red-hot. 
Yet  they  radiate  sufficient  heat  to  keep  the  temperature 
of  the  wires  below  that  required  for  the  passage  of 
flame  through  the  meshes,  and  the  lamp  continues  to 
burn  with  safety  if  kept  in  a  still  atmosphere. 

Stephenson's  lamp,  on  the  contrary,  only  admits  air 


34 


MINE    VENTILATION. 


§13. 


through  a  few  meshes,  the  glass  globe  preventing  the 
entry  of  any  air  or  gas  from  the  sides :  therefore  only 
a  small  proportion  of  gas  can  enter  the  interior  of  the 


FIG.  1. 


FIG.  2. 


FIG.  3. 


lamp  :  hence,  never  being  filled  with  flame,  the  wires  of 
the  gauze  remain  uninjured. 

Upon  these  principles,  various  modifications  have  been 
made  to  these  lamps,  until  they  now  number  a  hundred 


or  more. 


§13. 


MINE   VENTILATION. 


The  Clannj  lamp  consists  of  a  cylinder  of  glass  around 
the  flame,  and  a  wire-gauze  top.  A  better  light  is  pro- 
duced by  this  combination  (Fig.  2).  The  figures  show 
the  different  lamps,  with  permutation-lock  capable  of 


FIG.  4. 


FIG.  5. 


many  thousand  changes,  so  that  no  one  but  the  fire-boss 
can  unlock  the  lamps. 

The  Mueseler  lamp,  used  in  Belgium,  has   a   glass 
cylinder  for  the  light,  and  a  gauze  top  (Fig.  4).    There 


36  MINE  VENTILATION.  §13. 

is  a  copper  chimney  to  carry  off  the  smoke  of  the  burner, 
and  to  force  the  air  downward  between  the  glass  cylin- 
der and  the  chimney  upon  the  flame  of  the  burner, 
admitting  the  air  through  the  gauze  at  the  top. 

The  Boty  lamp  has  a  glass  cylinder  with  a  gauze  top, 
but  the  air  is  admitted  through  a  perforated  copper  ring 
at  the  bottom  of  the  lamp. 

The  Eloin  lamp  has  a  glass  cylinder,  admitting  air 
through  wire  gauze  near  the  bottom  of  the  lamp,  which 
is  thrown  against  the  burner  by  a  thin  copper  cap.  No 
other  air  enters  the  lamp,  and  consequently  it  is  easily 
extinguished.  Many  lamps  are  constructed  to  give  in- 
creased light  by  using  glass  globes.  The  Hall  lamp, 
with  diaphoretic  lens,  is  the  most  noteworthy,  on 
account  of  its  construction. 

The  Williamson  double  safety-lamp  is  a  Clanny  and 
Boty  lamp  combined  (Fig.  5). 

The  illuminating  power  of  the  various  lamps  in  most 
common  use  has  been  given  as  below;  the  standard 
being  a  wax  candle,  six  to  the  pound :  — 

Candle-power. 

Davy  lamp  (gauze)     .        .        .        .        .        .        .        .8 

Stephenson,  or  Georgie 1S£ 

Upton  and  Roberts 24| 

Clanny  (glass) 4J 

Parish  (gauze) 2| 

Mueseler's  (glass)      .        .        .        .        0        .        .        .  3-J 

Davy  (without  gauze) 2£ 


§14.  MINE   VENTILATION.  37 

14.  The  South  Shields  Committee  considered  the 
Davy  absolutely  unsafe. 

Mr.  Darlington  came  to  the  same  conclusion,  and  in 
answer  to  the  question,  "  Is  it  not  a  fact  that  dust 
will  fly  off  in  sparks,  and  that  one  spark  would  create 
an  explosion  ?  "  said,  "  There  are  very  many  instances 
of  accidents  taking  place  that  we  could  attribute  to 
nothing  else." 

Experiments  made  by  Mr.  N.  Wood  at  Killingworth 
Colliery,  in  1853,  to  ascertain  at  what  velocity  the  flame 
may  be  passed  in  an  explosive  mixture  of  fire-damp, 
were  as  follows:  — 

Davy  lamp  when  moving  13'  per  second. 

Clanny  lamp  went  out  at  IT  per  second. 

Boty  lamp  passed  flame  when  moving  at  15'  per  second. 

Hall  lamp  did  not  pass  flame  at  13'  per  second. 

Stephenson  lamp  was  extinguished  at  less  than  13'  per  second. 

Eloin  lamp  went  out  as  soon  as  it  was  filled  with  gas. 

Upton  and  Roberts  lamp  went  out  as  soon  as  it  was  filled  with  gas. 

The  Belgium  Commission,  appointed  by  the  king  in 
1868,  observed,  that  "  the  Davy  and  Deputy  lamps, 
when  exposed  for  two  minutes  to  an  explosive  mixture 
of  air  and  lighting-gas,  moving  at  a  velocity  of  4.264' 
per  second,  do  not  pass  the  flame  through  the  gauze ;  but, 
when  the  velocity  reaches  or  surpasses  7.38',  the  explo- 
sion is, always  produced  on  the  outside,  save  in  cases  of 


88  MINE    VENTILATION".  §  14. 

extinction  by  asphyxia,  caused  by  the  admission  of  a 
large  quantity  of  gas.  It  was  also  noticed  that  explo- 
sion takes  place  after  from  five  to  ten  seconds  when 
the  velocity  is  9.84',  and  after  from  two  to  five  seconds 
when  the  speed  is  19.68'. 

"  With  the  Mueseler  lamp,  out  of  a  one  hundred  and 
fifteen  experiments,  there  were  twenty-one  cases  of  com- 
plete extinction  at  a  velocity  of  19.68'  per  second. 

"  The  Morison  lamp  was  considered  of  very  compli- 
cated construction,  and  as  giving  a  very  bad  light  in 
stagnant  air.  Out  of  eleven  experiments  at  a  velocity 
of  19.68'  per  second,  these  lamps  caused  neither  exte- 
rior explosions,  nor  any  inflammation  of  gas  in  the 
exterior  cylinder. 

"  Rapid  currents  of  air  are  dangerous  when  their 
action  manifests  itself  by  the  crushing  of  the  flame 
upon  the  wicks :  indeed,  the  relative  security  of  the 
Mueseler  lamp  does  not  depend  alone  on  the  smallness 
of  the  section  of  the  chimney  at  the  top,  or  on  its 
height,  but  rests  essentially  in  the  regularity  of  the 
draught." 

The  North  of  England  Institute  of  Mining  Engi- 
neers, which  has  been  so  instrumental  in  the  further- 
ance of  mining  .knowledge,  appointed  a  committee,  who 
rendered  in  their  report  the  following  concerning  the 
velocity  at  which  the  various  lamps  would  explode :  — 


§  14  a.  MINE   VENTILATION.  89 

Per  second. 

Davy,  without  shield 8' 

Davy,  with  shield 12' 

Clanny 9' 

Stephenson 9' 

Mueseler 8' 

This  rather  conflicts  with  the  Belgium  Report,  as 
they  claim  the  Mueseler  lamp  passes  flame  as  easily 
as  the  Davy. 

14  a.  Fire-damp  may  be  detected  by  the  aid  of  a 
Davy  or  other  safety-lamp.  The  following,  taken  from 
the  Galloway  Royal  Society's  Journal  of  1876,  gives  the 
various  appearances  of  the  lamp-flame  when  brought 
in  contact  with  air  mixed  with  fire-damp :  — 

"The  wick  of  the  lamp,  having  been  carefully 
trimmed,  was  drawn  down  until  the  flame  presented 
the  appearance  of  a  small  blue  hemisphere  about  one- 
eighth  of  an  inch  high,  one-quarter  inch  diameter  at 
the  base,  and  having  a  conical  speck  of  yellow  in  the 
middle  near  the  top. 

"A  mixture  of  1  part  of  marsh-gas  with  16  parts  of 
air  gave  a  voluminous  waving,  spindle-shaped  blue  cap 
3|"  high. 

" 1  part  of  marsh-gas  with  18  parts  of  air  gave  a  cap 
2"  high,  which  burned  more  steadily. 

"  1  part  of  marsh-gas  with  20  parts  of  air  gave  a  cap 


40  MINE   VENTILATION.  §  15. 

1-^g"  high,  with  nearly  parallel  sides  to  about  two-thirds 
of  its  height,  and  then  tapered  to  a  point  at  the  top. 

"1  part  of  marsh-gas  with  25  parts  of  air  gave  a 
conical  cap  from  %  to  £"  high. 

"1  part  of  marsh-gas  with  30  parts  of  air  gave  a 
conical  cap  f"  high. 

"1  part  of  marsh-gas  with  40  parts  of  air  gave  a 
conical  cap  |"  high. 

"1  part  of  marsh-gas  with  50  parts  of  air  gave  a 
faint  cap  J"  high,  the  top  having  the  appearance  of 
having  been  broken  off. 

"With  1  part  of  marsh-gas  and  60  parts  of  air,  it 
was  hardly  possible  to  distinguish  any  thing  above  the 
small  oil-flame." 


CHAPTER  IV. 

PHYSICAL   PROPERTIES   OF   AIR   IN   MOTION. 

15.  WIND  is  air  in  motion ;  and,  as  air  is  matter,  it 
is  subject  to  the  laws  which  govern  matter.  No  particle 
of  matter  possesses  within  itself  the  power  of  changing 
its  existing  state  of  motion  or  rest.  When  a  body  is  at 
rest,  a  force  is  required  to  put  it  in  motion  ;  and,  when 
once  put  in  motion,  it  would  continue  to  move  on  for- 


§  15.  MINE   VENTILATION.  41 

ever  if  a  force  of  some  kind  were  not  opposed  to  it  to 
arrest  its  movement.  This  passive  property  of  air  is 
called  its  inertia,  and  may  be  defined  as  opposition 
to  change,  either  from  motion  to  rest,  or  vice  versa.  If 
the  air,  then,  had  no  inertia,  it  would  not  require  force 
to  give  it  motion,  nor  could  it  require  momentum. 
The  sailing  of  ships,  the  windmill,  the  tornado,  are 
familiar  examples  of  the  power  of  moving  air,  and,  con- 
sequently, proofs  of  its  inertia.  In  order  to  pass  air 
through  a  mine,  certain  force  must  be  expended ;  and 
this  force  is  what  we  are  now  about  to  examine.  It 
involves  a  consideration  of  the  resistances  to  be  over- 
come, such  as  area  of  the  airways,  obstructions  in  the 
airways,  and  the  friction  against  the  walls  or  sides  of 
the  airways.  When  air  travels  the  galleries  of  a  mine, 
it  rubs  against  all  the  exposed  surfaces.  This  rubbing 
gives  rise  to  the  resistance  called  "friction." 

Friction  of  air  in  mines  is  so  great,  that,  out  of  every 
ten  parts  of  power  employed  for  the  ventilation  of  a 
mine,  about  nine  of  the  ten  are  used  in  overcoming  the 
resistance  to  ventilation.  As  the  air  journeys  through 
the  mines  from  the  downcast  to  the  upcast,  it  not  only 
meets  the  rubbing-surface,  or  sides,  but  often  encoun- 
ters short  turns,  brattices,  etc.,  which  adds  greatly  to 
the  total  resistance  to  be  overcome. 

In   turning    sharp    corners,  the    air   strikes    square 


42  MINE  VENTILATION.  §16. 

against  the  face,  and  rebounds;  thus  hindering  the 
progress  of  the  air  following,  which,  in  turn,  goes 
through  the  same  operation,  and  hinders  the  air  follow- 
ing it.  It  is  therefore  preferable  to  have  well-rounded 
bends  of  large  radius,  as  they  produce  little  resistance 
in  comparison  with  elbows  or  square  bends.  The  con- 
sideration of  the  movements  of  air  in  mines  or  confined 
passages  involves  its  density,  the  area,  length,  and  pe- 
rimeter of  the  airways,  also  the  velocity  with  which  the 
air  travels. 

16.  To  find  the  perimeter  of  an  airway,  we  must  add 
together  the  bounding-lines.  The  perimeter  of  a  square 
airway  6'  X  6'  is  therefore  6  +  6  +  6  +  6  =  24'.  The 
perimeter  of  a  circle  is  its  circumference,  and  is  3.1416 
times  its  diameter:  hence  the  perimeter  of  an  airway 
six  feet  in  diameter  is  18.8496'.  The  sectional  area  of  an 
airway  is  found  by  multiplying  its  height  by  its  width. 
Thus  the  area  of  an  airway  5'  X  6'  is  30  square  feet. 
The  rubbing-surface  is  found  by  multiplying  the  perime- 
eter  by  the  length  of  the  airway. 

Problem. — What  is  the  rubbing-surface  of  an  airway 
500'  long,  with  an  area  of  &  X  6'? 

Solution.  —  6  +  6  +  6  +  6  =  24';  then  24'  X  500  = 
12,000  square  feet.  Am. 

As  friction  increases  according  to  the  rubbing-surface, 


§18.  MINE  VENTILATION.  43 

so  will  it  increase  or  decrease  according  to  the  bounding- 
lines  or  perimeter  of  the  airway.  From  this  it  becomes 
evident  that  the  form  which  has  the  least  perimeter 
will  have  •  the  least  rubbing-surface.  Above,  it  was 
shown  that  a  circular  airway  had  less  perimeter  than 
a  square  airway  of  the  same  diameter;  and  hence,  if 
the  two  airways  have  the  same  length,  the  circular  will 
have  less  rubbing-surface. 

17.  In  large  airways  the  friction  will  be  less  than  in 
smaller  airways  the  sum   of  whose  areas 

are  equal  to  the  area  of  the  large  airway. 

Let   us  suppose  an  airway  twelve  feet  ~ 
square  in  section :    its  area  will   be    144 

square   feet,   and   its    perimeter   12  -{-  12     I 

+  12  +  12  =  48'. 

Let  us  now  take  three  smaller  airways,  two  6'  X  6'  in 
section,  and  one  6'  X  12'  in  section.  The  aggregate  areas 
of  the  three  airways  will  be  36  -j-  36  +  72  =  144  square 
feet :  the  sum  of  the  perimeters  will  be  24  -J-  24  +  36 
=  84'.  Hence  we  see,  that,  while  the  large  airway  has 
the  same  area  as  the  aggregated  smaller  airways,  its 
perimeter  is  much  smaller  than  the  aggregate  perime- 
ters of  the  lesser  airways. 

18.  The    force    used    to    overcome    the    resistances 


44  MINE   VENTILATION.  §  la 

offered  to  the  passage  of  air  in  mines  is  estimated  in 
pounds  to  the  square  foot,  and  may  be  expressed  as  so 
much  head  of  air,  motive-column,  or  water-gauge.  The 
motive-column  has  already  been  treated  of,  so  our  atten- 
tion may  be  given  to  the  water-gauge.  The  water- 
gauge  is  an  instrument  used  to  measure  the  dynamic 
force  of  a  current  of  air.  It  consists  of  a  U-shaped 
tube  of  equal  area  throughout.  The  arms  are  about  six 
inches  long,  provided  with  a  scale  divided  into  inches 
and  fractional  parts  of  an  inch,  so  that  the  difference 
between  the  height  of  the  water  in  one  arm  of  the  tube 
and  that  of  the  other  may  be  measured.  One  arm  is 
placed  in  connection  with  the  air  passing  in  the  mine, 
while  the  other  is  open  to  the  air  away  from  the  mine. 
The  difference  in  water-level  will  indicate  the  drag,  or 
the  resistance  to  the  air  in  the  mine.  In  some  gauges, 
oil  is  substituted  for  water.  They  are  made  in  differ- 
ent shapes ;  but  the  principle  is  the  same  in  all.  The 
weight  of  one  cubic  foot  of  water  at  62°  F.  and  30" 
barometrical  pressure  is  62.32102  pounds  avoirdupois: 
62.32102  -4-  1728  =  0.036  pound  is  the  weight  of  one 
cubic  inch  of  water.  When  the  gauge  measures  one 
inch,  the  pressure  is  0.036  X  144  =  5.184,  or  5.2  pounds 
(nearly)  to  the  square  foot. 

Example.  —  Suppose  a  water-gauge  read  0.4",  what 
pressure  would  it  indicate? 

0.036  x  0.4  x  144  =  2.0734  pounds  to  the  square  foot. 


§  18.  MINE  VENTILATION.  45 

This  gauge  may  be  used  to  show  the  force  of  a  cur- 
rent produced  by  a  fan  or  by  a  furnace,  and  hence  is 
very  useful  as  a  check  to  the  furnace-man.  As  it  tells 
the  amount  of  resistance  to  the  air  in  the  air-courses, 
•their  state  or  condition  may  be  inferred.  If  the  pressure 
per  square  foot  exerted  by  the  motive-column  be  known, 
the  height  of  the  motive-column  may  be  determined. 

Problem.  —  Suppose  the  temperature  of  the  motive- 
column  be  62°  F.,  and  the  water-gauge  reads  0.4",  what 
is  the  length  of  such  motive-column  ? 

Solution.  — 100  cubic  feet  of  air  at  62°,  barometer 
30",  weigh  7.629  pounds.  1  cubic  foot  of  air  at  62°, 
barometer  30",  weighs  0.07629  pounds.  The  pressure 
per  square  foot  as  indicated  by  0.4"  water-gauge  is 
0.036  X  0.4  X  144  =  2.0736  pounds.  Dividing  the 
pressure  per  square  foot  by  the  weight  of  a  cubic  foot 

2  0736 

of  air  gives    '          =  27.28'  as  the  length  of  the  motive- 
column  in  feet. 

When  the  height  of  the  motive-column  is  known,  we 
may  find  the  velocity  of  the  air  in  feet  per  second 
which  the  motive-column  will  produce. 

Problem.  —  Suppose  the  motive-column  be  27.25'  in 
height,  what  velocity  per  second  will  it  produce?  A 
body  falling,  acted  "upon  by  gravity,  would,  according 
to  Eq,  2,  attain  a  velocity  represented  by  8.02V/i;  or 


46 


MINE  VENTILATION. 


18 


substituting  the  value  of  h,  which  in  this  case  is  27.25', 
we  have  8.02^27.25  =  42'  per  second. 


TABLE  IV. 
WATER-GAUGE. 


Length  of  mo- 

Water-gauge 
in  inches. 

Pressure  in  pounds 
per  square  foot. 
P=  0.036  x  W.G.  X144. 

tive-column  in 
feet  at  62°  F. 
P 

Velocity  of  the  air  in 
feet  per  second  due 
to  motive-column. 

0.0763- 

F-8WA. 

0.1 

0.5184 

6.79 

20.8921 

0.2 

1.0368 

13.58 

29.5938 

0.3 

1.5552 

20.37 

36.1702 

0.4 

2.0736 

27.16 

40.7416 

0.5 

2.5920 

33.95 

45.3130 

0.6 

3.1104 

40.74 

51.1676 

0.7 

3.6288 

47.53 

55.2578 

0.8 

4.1472 

54.32 

58.5460 

0.9 

4.6656 

61.11 

60.6262 

1.0 

5.1840 

67.90 

66.0046 

1.1 

5.7024 

74.69 

69.2928 

1.2 

6.2228 

81.48 

72.3404 

.3 

6.7392 

88.27 

75.2376 

.4 

7.2576 

95.06 

78.1950 

.5 

7.7760 

101.85 

80.9218 

.6 

8.2944 

108.64 

83.5684 

.7 

8.8128 

115.43 

86.0546 

1.8 

9.3312 

122.22 

88.6210 

1.9 

9.8496 

129.01 

90.7062 

2.0 

10.3680 

135.80 

93.1122 

3.0 

15.5520 

203.70 

114.3652 

4.0 

20.7260 

271.60 

132.1696 

5.0 

25.9200 

339.50 

147.9690 

6.0 

31.1040 

407.40 

161.8436 

7.0 

36.2880 

475.30 

174.8360 

§19.  MINE   VENTILATION.  47 

Table  IV.  gives  the  comparative  height  of  the  water- 
gauge  and  air-column  at  a  temperature  of  62°  F.,  with 
pressure  in  pounds  per  square  foot,  and  the  theoretical 
velocity  of  air  due  to  this  pressure.  This  table,  it  must 
be  remembered,  is  only  theoretically  true,  on  account 
of  the  enormous  power  required  to  overcome  friction 
to  the  passage  of  air  in  an  airway:  hence,  in  prac- 
tice, from  ten  to  twenty  times  this  amount  of  motive- 
column  is  required  in  order  to  produce  the  theoretical 
velocity. 

19.  "  Co-efficient  of  friction  "  is  a  term  used  to  repre- 
sent the  constant  resistance  met  with  by  air  during  its 
journey  through  the  mine.  This  resistance  must  be 
overcome  at  each  point,  before  the  air  can  pass  that 
point.  It  varies,  of  course,  under  different  conditions ; 
but,  the  smoother  the  rubbing-surface,  the  less  will  be 
this  resistance.  This  co-efficient  cannot  be  determined 
with  any  degree  of  certainty  except  by  actual  experi- 
ment ;  and  even  then  experimenters  differ  in  the  exact 
amount,  because  of  the  different  conditions  under  which 
the  experiments  were  made.  Sir  John  Atkinson,  after 
comparing  the  results  of  a  number  of  experimenters, 
took  an  average  between  their  results,  and  used,  as 
the  co-efficient,  0.26881  feet  of  air-column  of  the  same 
density  as  the  flowing  air.  He  appears  to  remain  in 


48  MINE   VENTILATION.  J  19. 

doubt  whether  the  mere  change  of  temperature  does  or 
does  not  affect  the  co-efficient  of  resistance.  As  it  is 
now  taken  for  granted  that  it  is  not  influenced  by  change 
of  temperature  (although  it  probably  is),  we  may,  for 
a  velocity  of  1,000  cubic  feet  per  minute,  consider  the 
friction  equal  to  an  air-column  0.26881  feet  in  height,  of 
the  same  density  as  the  flowing  air.  This  air-column  is 
equal  to  a  pressure  of  0.0217  pound  per  square  foot  of 
area  of  section  with  air  at  32°. 


Oi26881  =  0.0217  pound  per  square  foot. 


459      32 


When  we  consider  the  air-column,  we  may  use  the 
co-efficient  0.26881;  afterwards,  if  we  desire,  we  may 
reduce  the  height  of  the  air-column  thus  found  to 
pounds  per  square  foot,  as  above. 

We  may  shorten  this  work,  however,  by  using  0.0217 
pound  per  square  foot  of  area  for  every  square  foot'  of 
rubbing-surface  exposed  to  the  air-current,  at  a  velocity 
of  1,000  feet  per  minute,  or  0.0000000217  pound  for  a 
velocity  of  1  foot  per  minute. 

We  must  also  bear  in  mind,  that,  while  we  use  h  in 
the  following  formulas  for  the  air-column  which  by  its 
weight  will  produce  pressure,  we  use  0.0217  to  find  the 
pressure,  P,  direct,  considering  all  air  in  passing  to  have 
the  same  co-efficient,  viz.,  0.0217. 


§20. 


:,IINE   VENTILATION. 


49 


Mr.  Thomas  and  several  other  writers  consider  this 
co-efficient  as  much  too  large:  be  that  as  it  may,  we 
can  see  at  present  no  reason  why  it  should  be  rejected, 
until  the  experiments  already  referred  to  approach 
more  nearly  to  each  other  in  their  results.  The  co- 
efficients in  practice  can  never  be  the  same  in  different 
mines ;  but  they  may  approach  each  other  by  making 
the  airways  as  smooth,  and  free  from  obstructions,  as 
possible. 

PRESSURE. 

20.  Some  of  the  formulas  relating  to  the  friction 
of  air  in  mines,  adopted  by  Mr.  Atkinson  in  his  book 
on  "  Mine  Ventilation,"  will  be  retained  in  this  treatise, 
so  that  any  one  studying  this  book  will  better  under- 
stand his  method  of  reasoning. 

Let  h  =  motive-column  in  feet. 

p  =  pressure  per  square  foot  due  to  weight  of  h. 

a  =  sectional  area  in  square  feet. 

Jc  =  co-efficient  of  friction  =  0.0217  pounds  per  square 
foot  of  area  of  section  for  a  velocity  of  1000 
feet  per  minute  with  air  at  32°.  It  is  to  he 
taken  in  the  same  terms  or  unit  as  p  is  taken  in. 

s  =  rubbing-surface. 

v  =  the  velocity  of  the  air  in  thousandths  of  feet  per 
minute,  1000  feet  per  minute  being  taken  as 
the  unit  of  velocity. 


50  MINE   VENTILATION.  §  21. 

The  total  pressure  is  found  by  the  formula 

(6)  pa  =  Jcsv12 

which,  expressed  in  words,  gives  us  the  following  rule : 
To  find  the  total  pressure  due  to  the  friction  of  air 
passing  through  an  airway,  multiply  the  co-efficient  of 
friction  by  the  rubbing-surface,  and  the  product  by  the 
square  of  the  velocity ;  or,  pressure  being  known,  mul- 
tiply the  pressure  per  square  foot  by  the  area  of  the 
airway. 

21.   To  find  the  pressure  per  square  foot, 

Tcsv* 

(7)  P=— , 

divide  the  total  pressure  by  the  area  of  the  airway. 

By  the  clearing  of  fractions,  division,  and  other  alge- 
braical operations,  we  may  find  formulas  which  corre- 
spond to  rubbing-surface  and  velocity,  and  also  find  the 
co-efficient  of  friction.  These  formulas  embrace  only 
pressure  due  to  friction,  and  not  that  due  to  the  crea- 
tion of  velocity:  hence  they  will  be  more  correct  for 
long  than  for  short  airways.  The  symbols  in  these 
formulas  are  so  connected  with  each  other,  that,  when 
a  sufficient  number  of  them  are  known,  those  unknown 
may  be  found.  To  show  the  application  of  these  for- 


§  21.  MINE  VENTILATION.  51 

mulas,  suppose  we  have  an  airway  8'  X  T',  2,000  feet 
long,  with  the  air  travelling  at  the  rate  of  15  feet  per 
second  through  it.  What  is  the  resistance  due  to  fric- 
tion, or  the  motive-column  required  to  overcome  friction 
in  the  airway  ? 

a  =    8x7  =  56  square  feet. 
&  =  0.26681. 

s=    8  +  8  +  74-7  =  30  x  2000  =  60000  square  feet. 
v2  =  15  x  60  =  900'  per  minute,  or  0.9  of  1000  feet  per 
minute,  which  squared  is  equal  0.81. 

Substituting  the  numerical  values  of  these  symbols 

iii  (T), 

_  0.26881  X  60000  X  0.81  _  ^^ 

56 

of  air-column  as  the  pressure  required  to  overcome  the 
friction,  and  produce  circulation.  Taking  the  air  at 
62°  F.,  one  cubic  foot,  with  the  barometer  at  30  inches, 
would  weigh  0.0763  of  a  pound.  If  we  now  multiply  this 
motive-column  by  the  weight  of  a  cubic  foot  of  the  air 
it  is  composed  of,  and  divide  the  product  by  5.2  pounds, 
—  the  pressure  per  square  foot  when  the  water-gauge 
is  one  inch,  —  we  may  find  the  water-gauge  due  to  this 
pressure,  and  also  the  pressure  on  each  square  foot. 

0.0763  X  233.288 


5.2 


=  3.42"  water-gauge, 


52  MINE   VENTILATION.  §  21. 

The  pressure  per  square  foot  is  17.7  pounds.      From 
tliis  we  may  obtain  a  formula  for  water-gauge. 


ksv2 


The  same  result  may  be  obtained  by  multiplying  the 
length  of  the  motive-column  by  the  weight  of  a  cubic 
foot  of  air  of  the  same  density,  thus  obtaining  the 
pressure  direct  without  first  finding  the  water-gauge. 

The  quantity  of  air  passing  may  be  found  by  multi- 
plying the  velocity  in  feet  per  minute  by  the  area  of 
airway  in  square  feet,  or 


u 

(9)  <}  =  „»  =  - 

The  u  in  the  last  equation  represents  units  of  work, 
foot-pounds  applied  to  circulate  the  air. 

(10)  u  =  Q  X  p  =  vpa  =  HP  x  33000. 

The  HP  in  the  last  formula  stands  for  horse-power  of 
ventilation. 


u 

33000  ~  33000' 


§  22.  MINE  VENTILATION.  53 

When  we  represent  the  length  of  an  airway  by  Z,  the 
rubbing-surface  by  s,  the  perimeter  by  0,  we  have 

(12)  s  =  o  X  I. 

(13)  -  1  =    . 


CHAPTER  V. 

THE  LAWS   AFFECTING  AIE,  IN   MINES. 

22.  THE  laws  affecting  the  circulation  of  air  through 
mines  or  confined  passages,  such  as  gangways,  etc., 
have  been  ascertained  principally  by  such  eminent  men 
as  Magnus,  Regnault,  Gay-Lussac,  Daubisson,  Peclet, 
and  others,  and  are  as  follows  :  — 

1.  The  volume  assumed  by  a  given  weight  of  air  is 
inversely  proportional  to  the  pressure  on  each  unit  of 
surface  under  which  it  exists,  so  long  as  the  tempera- 
ture remains  unaltered.  Consequently,  if  we  take  a 
cubic  foot  of  air  under  a  pressure  of  five  pounds,  it  will 
only  be  one-half  a  cubic  foot  under  a  pressure  of  ten 


54  MINE   VENTILATION.  §  22 

pounds,  and  one-third  of  a  cubic  foot  under  a  pressure 
of  fifteen  pounds. 

2.  When    the   pressure   is   constant,   the   volume   is 
uniformly  increased  in  the  ratio  of  ^J^  part  for  each 
additional  degree  of  heat,  Fahrenheit's  scale. 

3.  When  air  is  discharged  through  orifices  offering 
no  sensible  frictional  resistance,  the  result  is  sixty-five 
per  cent  of  the  quantity  due  to  the  velocity  multiplied 
by  the  area  in  case  of  a  thin  plate ;  ninety-three  per 
cent  in  case  of  a  short  cylindrical  tube ;  and  ninety-five 
per  cent  when  the  tube  is  conical,  and  the  area  taken 
from  the  small  end.     This  contraction  of  the  flowing 
air,  which  is  similar  to  that  which  takes  place  when 
water  is  discharged  through  pipes  under  the  same  con- 
ditions, has  the  effect  of   reducing  the  quantity  dis- 
charged in  a  given  time  below  that  which  would  be  due 
to  the  velocity,  if  it  existed,  over  an  area  equal  to  that 
of  the  orifice  or  tube.     This  contraction  of  the  flowing 
air  is  termed  the  "  vena  contracta." 

4.  When  air  is  impelled  through  a  confined  passage, 
the  pressure  or  head  of  air-columri  required  for  its  pro- 
pulsion is   proportional    to   the   square  of  the  velocity; 
so  that  to  double  this  velocity  there  must  be  four  times 
the  head ;  to  treble  it,  nine  times  the  head ;  etc. 

(0)  Ventilating  pressure,  jo,  or  ("head  of  air,"  or 
"motive-column,"  reduced  to   pounds)  total  pressure, 


§  22.  MINE  VENTILATION.  55 

pa  or  ha,  and  ventilating  power,  P,  are  separate  and 
distinct  terms.  Ventilating  pressure,  or  simply  pressure, 
is  the  force  applied  to  each  square  foot  of  area  of  sec- 
tion to  produce  ventilation.  That  this  pressure  varies 
as  the  square  of  the  velocity,  as  stated  above,  may  be 
illustrated  by  the  following  :  — 

Problem.  —  When  a  mine  is  passing  20,000  cubic  feet 
of  air  per  minute  with  a  pressure  of  2.6  pounds  per 
square  foot,  as  indicated  by  0.5-inch  water-gauge,  what 
will  be  the  pressure  if  the  mine  pass  40,000  cubic  feet 
per  minute?  This  principle  may  be  resolved  simply 
into  finding  a  fourth  proportional  ;  thus,  — 


(20000)2:  (40000)2  ::p:? 

(2)2  :  (4)2  ::  2.6  :  10.4  pounds.     Ans. 

(5)  The  total  pressure  is  the  ventilating  pressure,  p, 
multiplied  by  the  area  of  section  a  of  the  airway  in 
square  feet.  Thus,  if  the  sectional  area  of  the  above 
airway  were  64  square  feet,  and  the  pressure  0.5-inch 
water-gauge,  the  total  pressure  would  be  pa  =  64  X 
2.6  —  166.4  pounds. 

(tf)  Ventilating  power  is  power  used  to  obtain  ven- 
tilating pressure.  This  power,  P,  varies  as  the  cube  of 
the  velocity  of  the  air-current.  By  this  we  mean,  that, 
if  we  can  circulate  a  quantity  of  air  with  2  HP,  we 


56  MINE   VENTILATION.  §  22. 

must  use  8  HP  if  we  wish  to  circulate  a  double  quan- 
tity. This,  as  can  be  readily  seen,  is  a  very  important 
factor  in  fiery  mines  ;  as  the  engine  working  the  fan  or 
the  furnace  may  be  called  upon  at  any  time  to  do 
double  and  maybe  threefold  duty,  in  case  blowers 
or  barometrical  differences  allow  an  unusual  amount  of 
gas  to  be  given  off. 

Problem.  —  Suppose  we  have  20,000  cubic  feet  of  air 
passing  with  a  water-gauge  of  0.5  inches,  equal  to  a 
pressure  of  2.6  pounds  per  square  foot,  what  will  be  the 
ventilating  power,  P,  if  we  double  the  ventilation  ? 

Solution.  —  20,000  X  2.6  =  units  of  work  =  52,000 
foot-pounds.  As  there  are  33,000  foot-pounds  in  1-horse 
power,  we  have 

u       =  52000  p 

~  33000  ~  33000  ~ 

Again:  from  22  (a)  we  find  that  to  double  the  quantity 
we  must  employ  four  times  the  pressure  :  hence 

P=  40000  x  2.6  X  4  =  416000  foot-pounds  =  u 
and 


_   __1 
33000        33000  " 

or  eight  times  the  power  in  the  first  case. 

5.  In  airways  of  the  same  sectional  area,  the  pressure 


§22. 


MINE  VENTILATION. 


57 


required  to  propel  air  is  proportional  to  the  length  of 
the  passage,  or,  in  other  words,  there  must  be  double 
pressure  for  double  distance. 

Problem.  —  Suppose  we  have  an  airway  2,000  feet 
long,  and  another  4,000  feet  long,  of  the  same  area; 
the  pressure  being  2.6  pounds  per  square  foot  in  the 
shorter.  What  will  be  the  pressure  necessary  to  over- 
come the  resistance  in  the  longer  airway  ? 

2000:  4000::  2.6:? 

1:2::  2.G  :  5.2  pounds.     Ans. 

6.  The  pressure  required  to  propel  air  through  con- 
fined passages  is  proportional  to  the  perimeter  of  the 
passages ;   the  length  and  other  data  remaining   con- 
stant.    Thus,  if  we  have  an  airway  4  feet  square,  and 
another  8  feet  square,  with  a  pressure  of  2.6  pounds 
per   square  foot  for  the  4-foot  airway,  we  shall  have 
5.2  pounds  for  the  8-foot  airway,  or 

1:2::2.G:5.2.     Ans. 

7.  The   pressure  required  on  each  unit  of  surface, 
square  inch  or  square  foot,  to  propel  air  through  a  con- 
fined passage,  is  inversely  proportional  to  the  sectional 
area  of  the  passage,  when  all  other  things  are  equal ; 
so  that,  the  greater  the  area  exposed  to  the  pressure, 
the  less  is  the  amount  of  pressure  required  for  each 


58  MINE   VENTILATION.  §  22. 

unit  of  surface.  This  is  of  great  importance  in  venti- 
lation, as  it  allows  of  a  greater  quantity  .of  air  passing 
with  the  expenditure  of  less  power  than  any  other 
means  known.  This  principle  is  the  one  upon  which 
the  splitting  of  air  is  reasoned.  In  the  case  of  the 
eight-foot  and  four-foot  passages  in  (6),  while  the  former 
required  double  the  amount  of  pressure  for  its  double- 
sized  perimeter,  that  pressure  would  propel  four  times 
the  quantity:  otherwise  the  same  expenditure  of  power 
on  air  in  a  four-foot  passage  would  propel  double  the 
quantity  it  would  force  through  a  two-foot  passage, 
or  an  equal  quantity  would  be  propelled  by  half  the 
power.  The  entire  mass  of  moving  air  in  an  airway 
may  be  considered  as  a  column  of  water  passing  through 
a  pipe,  exposing  a  certain  amount  of  surface  to  resist- 
ance, and  hence  requiring  a  fixed  amount  of  pressure 
acting  upon  its  sectional  area  to  overcome  such  resist- 
ance when  the  velocity  is  constant:  therefore,  the 
greater  the  area  of  section,  the  less  the  amount  of 
pressure  requisite  for  each  individual  unit  of  such  area 
in  order  to  make  up  the  gross  amount  of  such  pressure 
required.  The  steam-engine  piston  will  require  less 
pressure  per  square  inch  to  produce  a  given  force  as 
the  area  of  the  piston  is  greater,  and  vice  versa.  Taking 
the  areas  given  in  (6),  we  have  the  following  propor- 
tion :  — 

64: 16::  2.6:  0.65.     Ans. 


§23. 


MINE   VENTILATION. 


59 


8.  The  pressure  required  to  overcome  the  frictional 
resistances  encountered  by  air  in  passing  through  a  con- 
fined passage  has  been  found  to  vary  with  the  nature 
of  the  material  composing  the  inner  surface  of  the  air- 
way to  which  the  moving  air  is  exposed  in  its  route, 
as  well  as  the  mechanical  state  of  its  surface :  in  other 
words,  the  smoother  the  rubbing-surface,  the  less  the 
resistance. 


CHAPTER  VI. 


LAWS    AFFECTING    THE    MOVEMENT   OF   AIR   IN   MINES, 
CONTINUED. 

23.  1.  IN  airways  of  the  same  sectional  area,  and 
which  only  differ  in  length,  "  the  volume  and  velocity 
of  air-currents  are  inversely  proportional  to  the  square 
roots  of  the  lengths." 

Problem.  —  When  an  airway  4'  X  5'  area,  and  length 
of  4,000  feet,  passes  20,000  cubic  feet  of  air  per  minute, 
what  will  another  airway  1,000  feet  in  length,  with  the 
same  area  and  pressure,  pass  ? 


1000  :  V4000  ::  20000  :  x 

I  :  V3  ::  20000  :  40000  cubic  feet. 


Ans. 


60  MINE   VENTILATION.  §  23. 

Again :  the  velocity  in  the  second  airway  will  be 

/ , 20000 

V/l  000:^4000::-^-  :x 

that  is 

V^I :  V^I ::  1000  :  a?, 
or 

1  :  2  ::  1000  :  2000'  per  minute.     Ans. 

That  is,  the  volume  and  velocity  in  the  1,000-foot  air- 
way are  twice  the  volume  and  velocity  in  the  4,000-foot 
airway. 

2.  The  volume  passing  through  airways  of  similar 
form  but  unequal  size  will  be  greater  as  the  area  of 
section  is  greater,  other  data  being  the  same ;  or,  the 
pressure  and  other  data  remaining  constant,  the  quan- 
tity will  be  directly  proportional  to  the  areas :  — 

a:A::v:V. 

3.  The  volume  passing,  when  areas  and  other  data 
are   equal,  is   inversely  proportional  to  the  perimeter 
of  the  sections  of  the  airways.     The  circle  passes  the 
greater  quantity  of  two   airways,  one   of  which  is  a 
square  with  a  side  equal  to  the  diameter  of  the  circle. 
(See  §16.) 

4.  The  quantity  or  volume  of  air  passing  through  an 
airway  varies  as  the  square  root  of  the  rubbing-surface. 


§24. 


MINE   VENTILATION. 


61 


L 


5.  Friction  diminishes  in   proportion  to  the  square 
root  of   the  velocity,  and  increases  according  to  the 
square  of  the  velocity  ;  i.e.,  friction  varies  as  the  square 
of  the  velocity. 

6.  Pressures  are  proportional  to  the  squares,  and  the 
powers  are  proportional  to  the  cubes,  of  the  quantities 
of  air  passing  through  airways. 

7.  The  quantity  of  air  passing  through  airways  of 
different  areas,  other  things  being  equal,  is  according 
to  the  square  root  of  the  area  multiplied  by  the  area. 

PROBLEMS  TO  ILLUSTRATE   THE  FOREGOING  LAWS. 

24.  («)  If  20,000  cubic  feet  of  air  can  be  produced 
in  an  airway  of  60  feet  area  with  a  certain  pressure, 
how  much  air  will  the  same  pressure  produce  in  an 
airway  of  30  feet  area? 

Assume  the  perimeters  to  be  32  feet  for  60-foot  air- 
way, and  22  feet  for  30-foot  airway.  Had  the  relation- 
ship which  existed  between  the  perimeter  and  the  area 
of  the  larger  airway  been  maintained  in  the  smaller 
airway,  then  the  quantity  of  air  flowing  through  the 
latter  would  be  directly  proportional  to  its  area  (2), 
pressure,  etc.,  remaining  constant.  That  is  to  say,  the 
ratio  of  the  area  to  the  perimeter  of  the  larger  airway  is 
as  60  to  32.  In  the  smaller  airway  we  have  one-half  the 
area ;  and,  had  the  smaller  perimeter  been  one-half 


62  MINE   VENTILATION.  §24. 

the  larger,  then  the  ratio  would  have  been  unaltered, 
and  the  quantity  of  air  would  have  been  one-half 
also  (3).  But,  instead  of  the  smaller  perimeter  being 
16  feet,  it  is  22  feet.  Now,  the  problem  resolves  itself 
simply  into  finding  a  fourth  proportional  ;  and,  bearing 
in  mind  (4)  that  the  quantity  varies  inversely  as  the 
square  root  of  the  rubbing-surface,  we  have, 


V/22  :  V^Te  ::  10000  cubic  feet  :  x 
.•.     x  =  8528  cubic  feet  per  minute.     Ans. 

In  the  above  calculation  the  length  of  the  airway 
is  taken  as  unity  ;  because  any  given  length  will  be 
a  factor  common  to  both  terms  of  the  first  ratio,  and 
hence  may  be  eliminated. 

To  prove  this  method  of  reasoning,  we  may  work  it 
out  according  to  Atkinson's  method  :  — 

Taking  the  length  of  both  airways  as  1,000  feet,  we 
have,  for  the  larger, 

s  =  32000  square  feet. 

20000       n_   ' 
v  =  —      -  =  O.ooo 
60 

in  thousandths  of  feet  per  minute.      Substituting  in 
formula  (7) 

0-26881  x  32000  X  (0.3  X  0.3) 


a  ~60 

=  15.9295'  of  air-column. 


§  24.  MINE  VENTILATION.  63 

For  the  smaller  airway, 

s  =  20000, 
and 

15.9295  X  30          477.885 


0.26881  X  20000       5913.82 


=  0.0808082 


.-.  v  =  Y'0.  0808082  X  1000  =  284.27  feet  per  minute  ; 

and,  as  the  quantity  passing  is  found-  by  (9),  §  21,  we 
have  284.27'  X  30  =  8528  cubic  feet  per  minute. 

Problem  (£>).  —  Suppose,  now,  we  take  two  airways 
whose  lengths  are  each  35  units,  and  which  have  the 
same  area  ;  the  quantity  of  air  passing  through  each 
being  9,000  cubic  feet.  What  will  each  circulate  of  the 
total  amount,  if  their  lengths  be  in  the  ratio  of  3  to  4  ? 

Solution.  —  From  (1)  and  (4),  §  23,  we  deduce  two 
proportions,  —  one  for  the  longer,  and  one  for  the  shorter 
airway.  Now,  if  these  airways  were  in  the  ratio  of  3 
to  4  in  length,  then  one  would  ,be  30  units  and  the 
other  40  units  in  length,  and  the  quantities  of  air  which 
would  flow  through  them  under  the  same  conditions 
may  be  computed  thus  :  — 

For  the  longer  airway 

V/40:\/35::  9000  :  x 
or 


and 

8  :  ^56  :  :  9000  :  8418.     Ans. 


64  MINE   VENTILATION.  §  24. 

For  the  shorter  airway 

:  ^35  ::  9000  :  x,  or  06  :  ^7  ::  9000  :  x 


and  hence 

G  :  V^42  ::  9000  :  9721  cubic  feet.     Ans. 
Total, 

8418  +  9721  =  18139  cubic  feet. 
Proof, 

03:^::  8418:  9721 
V/4:V^3::  9721:  8418. 

(e)  Suppose  we  have  two  airways  of  the  same  sec- 
tional areas  and  lengths,  each  passing  9,000  cubic  feet 
as  before.  Suppose  each  to  have  4  units  of  lengths.  If 
one  of  these  airways  be  shortened  to  unity,  it  will  have 
but  J  the  rubbing-surface  of  its  former  length  ;  and  the 
volume  of  air  will  be,  according  to  (1),  found  thus  :  — 

VI:  0±::9000:  18000. 

Again  :  let  the  length  of  one  of  the  airways  be  in- 
creased fourfold,  then  the  volume  of  air  will  have  four 
times  the  rubbing-surface,  and  by  (4)  we  have 

VTG:V/4::9000:  4500. 

(The  above  illustrates  in  a  striking  manner  the  effect 
that  rubbing-surface  has  of  diminishing  the  flow  of  air 
through  a  gallery.) 


§  24.  MINE   VENTILATION. 

The  total  volume  will  be  22,500  cubic  feet ;  and,  not- 
withstanding the  rubbing-surface  is  more  than  doubled, 
the  volume  is  only  increased  by  twenty-five  per  cent. 
The  pressure  required  to  circulate  the  air  under  each 
set  of  conditions  is  precisely  the  same ;  for  the  smaller 
rubbing-surface  multiplied  by  the  square  of  the  highest 
velocity  is  equal  to  the  greater  rubbing-surface  mul- 
tiplied by  the  square  of  the  lower  velocity ;  thus 
/9000\2  *  onocnn  A  /4500\2  onoKAA 

(w)  x  4 = 202500' and  (-W)  x  16  = 202500' and 

f  — - — -  j  X  1  =  202500,  if  we  assume  the  areas  of  the 

above  to  be  40  square  feet. 

That  the  pressure  remains  the  same  may  be  shown 
by  Atkinson's  method :  — 

Let  the  above  unit  of  length  be  assumed  as  100  feet, 
then  equal  airways  are  400  feet  in  length ;  and,  if  we 
assume  the  area  and  perimeter  to  be  respectively  25 
and  20  feet,  we  may  find  the  pressure,  thus :  — 

n.      ,       0.26881  x    400  X  20  X  0.1296 

(1)  h  =  -  —  —=  11.148  ft.  head. 

,0v      7       0.26881  x     100  x  20  x  0.5184 

(2)  h  =  -         — —        -=  11.148  ft.  head. 

Zo 

,^  ,   0.26881  x  1600  X  20  x  0.0324 

(3)  h  =  -  -=  11.148ft.  head. 


66  MINE   VENTILATION.  §  24. 

(c?)  If,  through  two  airways  6  feet  square,  9,000 
cubic  feet  of  air  flow  per  minute,  and  one  of  them  be 
altered  in  section  to  a  circle  (its  area  being  unaltered), 
then  the  quantity  of  air  circulating  may  be  computed, 
thus  :  — 

V21.27  :  Y^24  ::  9000  :  95GO.     Ans. 


The  volume  flowing  through  both  airways  would  now 
be  18,560  cubic  feet  ;  but,  in  the  event  of  this  quantity 
being  reduced  to  18,000  cubic  feet,  the  circular  airway 
would  have  more  flowing  through  it  than  the  other. 

(e)  What  volume  of  air  would  flow  through  an  air- 
way 5  feet  square,  if  6,000  cubic  feet  flow  through  an 
airway  10  feet  square,  the  pressure  and  length  being 
the  same? 

Solution.  —  The  volume  varies  as  the  square  root  of 
the  rubbing-surface  (§  23,  4),  and  directly  as  the  area 
(§  23,  2)  :  hence  we  have  a  compound  proportion, 

SI'S-"-- 

or 

V/20  x  25  X  6000 

x  =  -  —  -f=  —     -  =1061  cubic  feet.     Ans. 
V40  x  100 

It  may  be  reasoned  thus:  as  the  area  was  reduced  one- 
fourth,  the  resulting  volume  would  be  one-fourth  also, 


§25.  MINE   VENTILATION.  67 

namely,  1,500  cubic  feet  ;  but,  instead  of  the  perimeter 
being  reduced  to  one-fourth,  that  is,  10  feet,  it  is  only 
reduced  to  20  feet.  The  volume  may  now  be  found, 
thus  :  — 


or 

V/2  :  V^T  :  :  1500  :  1061  cubic  feat.     Ans. 

(h)  Suppose  we  have  a  pressure  equivalent  to  40  HP, 
giving  a  circulation  of  120,000  cubic  feet  per  minute: 
what  quantity  will  a  pressure  equivalent  to  32  HP 
give  ?  From  §  23,  6,  we  have 

^40  :  V32  :  :  120000  :  111398  cu.  ft.  per  minute.     Ans. 

Proof.     (111398)3  :  (120000)3  :  :  32  :  40.     Ans. 

(i)  Suppose  we  have  a  pressure  equivalent  to  32 
pounds  per  square  foot,  circulating  107,350  cubic  feet 
per  minute,  what  pressure  will  circulate  120,000  cubic 
feet? 

Solution.  J107350)2  :  (120000)2  :  :  32  :  40.     Ans. 

Proof.     ^40:^32::  120000  :  107350.     Ans. 

25.  From  the  proof  of  the  last  problem  we  see  that 
air  may  be  measured  by  the  pressure,  or,  what  amounts 
to  the  same,  the  water-gauge,  and  we  can  say  the  quan- 


68 


MINE   VENTILATION. 


§25. 


tity  of  air  passing  in  a  mine  is  according  to  the  square 
root  of  the  water-gauge. 

Problem.  —  Suppose  we  have  30,000  cubic  feet  of  air 
passing  when  the  water-gauge  is  1.6  inches,  what  quan- 
tity will  pass  with  2.5  inches  of  water-gauge  ? 


or 


:  :  30000  :  x 


1.2649  :  1.5811  :  :  30000  :  37500  (nearly)  cubic  feet. 
TABLE  Y. 

SQUARE  ROOT  OF  WATER-GAUGE. 


W.  G. 

JW.G. 

W.G. 

^W.G. 

W.G. 

^W.G. 

0.1 

0.3162 

.2 

1.0954 

2.3 

1.5165 

0.2 

0.4474 

.3 

1.1401 

2.4 

1.5491 

0.3 

0.5477 

.4 

1.1832 

2.5 

1.5811 

0.4 

0.6324 

.5 

1.2247 

2.6 

1.6144 

0.5 

0.7071 

.6 

1.2649 

2.7 

1.6431 

0.6 

0.7745 

.7 

1.3038 

2.8 

1.6733 

0.7 

0.8366 

.8 

1.3416 

2.9 

1.7029 

0.8 

0.8944 

.9 

1.3784 

3.0 

1.7320 

0.9 

0.9486 

2.0 

1.4142 

3.5 

1.8460 

1.0 

1.0000 

2.1 

1.4491 

4.0 

2.0000 

1.1 

1.0488 

2.2 

1.4832 

4.5 

2.1213 

§26.  MINE  VENTILATION.  69 


CHAPTER  VII. 

VENTILATION   OF   SINGLE  PITS  OR   DRIFTS. 

26.  DURING  the  sinking  of  shafts,  or  driving  of  drifts, 
the  ventilation  is  caused  by  the  diffusion  of  gases,  and 
by  the  temperature  of  the  atmosphere  or  outer  air  and 
that  of  the  mine.  It  can  hence  only  be  temporary, 
becoming  insufficient  as  soon  as  certain  variable  and 
often  very  small  depth  is  attained,  unless  recourse  be 
had  to  some  other  means.  The  simplest  mode  of 
attaining  this  end  consists  in  dividing  the  pit  by  a 
wooden  brattice,  so  that  the  warm  air  may  ascend  one 
side,  while  the  cool  air  will  descend  the  other.  If 
this  does  not  produce  circulation,  it  can  generally  be 
attained  by  connecting  one  side  of  the  brattice  with 
a  high  chimney,  which,  by  establishing  a  difference 
between  the  levels  of  the  orifices,  causes  a  natural 
circulation  of  air.  If  compressed  air  or  steam  be  used 
for  drills,  or  if  pumps  be  suspended  in  the  pit,  the 
chimney  will  be  unnecessary.  A  fire  may  be  placed  at 
the  bottom  of  the  pit  to  warm  the  air  on  one  side  the 
brattice,  or  a  small  hand  centrifugal  fan  be  employed 
to  advantage.  In  drifts,  the  brattice  is  placed  parallel 
to  the  axis,  and  disposed  in  a  horizontal  or  vertical 


70  MINE  VENTILATION.  §  26. 

plane  as  better  suits  the  case.  When  placed  in  the 
vertical  plane,  one  of  the  compartments  may  be  used 
as  a  tramway  and  intake  for  the  air :  the  other,  com- 
municating  with  the  upcast  pit,  is  used  entirely  as  a 
return.  When,  a  horizontal  brattice  is  used,  it  may  be 
at  the  feet  or  head  of  the  workmen. 

In  this  case  the  brattice  is  used  to  facilitate  the 
ventilation  of  drifts,  and  also  the  driving  and  sink- 
ing of  internal  drifts,  by  putting  the  airway  one  side 
of  the  brattice  in  communication  with  the  downcast. 
Within  the  last  fifteen  years,  miners  have  superseded 
this  method,  wherever  practicable,  by  "brattice-cloth" 
nailed  to  a  series  of  props.  The  cloth  is  made  imperme- 
able to  the  air  by  being  covered  with  tar,  or  dipped  in  a 
solution  of  soda  silicate.  Treated  in  the  latter  manner, 
it  is  rendered  incombustible,  as  well  as  impermeable  to 
the  air.  Brattice-cloth  is  only  used  to  secure  temporary 
ventilation,  and  should. never  be  permitted,  except  at 
the  face,  or  where  it  is  subjected  to  constant  scrutiny,  as 
it  may  decay ;  and  inattention  to  its  repair  or  renewal 
might  cause  serious  accidents.  Another  method  of 
conducting  air  into  drifts  is  by  a  continuous  wooden 
box.  This  box  may  be  placed  in  any  position  where 
it  will  be  out  of  the  way,  with  one  of  its  extremities 
connected  with  a  chimney,  if  it  be  driven  from  the  day  ; 
or  with  the  return  airway,  if  the  sinking  or  drift  be 


§26.  MINE  VENTILATION.  71 

made  in  the  mine.  Air-boxes,  whose  use  is  consistent 
with  economy,  if  of  a  great  length,  will  not  supply 
sufficient  volume  of  air,  owing  to  the  great  absorption 
of  the  "  motive-column  "  by  friction.  Tubes  are  made 
of  other  materials  than  wood,  such  as  zinc,  canvas,  and 
paper ;  but  they  have  never  come  into  great  demand. 
These  air-boxes  or  tubes  may  be  used  to  convey  fresh 
air  to  the  face  of  the  workings,  or  return  the  foul  air. 
It  is  preferable  to  employ  them  for  the  first  method, 
rather  than  for  the  second;  for  more  air  is  thrown 
upon  the  face  of  the  workings,  because,  when  suction 
is  employed,  the  air  will  leak  through  the  box  before 
it  reaches  the  mouth  of  the  box  at  the  upcast,  also  the 
contraction  of  the  air-vein  at  the  entry  of  the  box  must 
be  greater  in  the  suction  than  in  the  forcing  principle. 

Again :  the  air  will  be  purer  when  delivered  to  the 
face  fresh  from  the  day,  for  by  suction  it  must  neces- 
sarily bring  to  the  face  gases  and  foul  air  met  with 
along  fts  route.  It  is  also  evident  that  the  diffusion  of 
fire-damp  by  the  mechanical  action  of  the  air  will  be 
better  by  the  forcing-system.  When  the  excavation 
has  attained  the  extreme  point  where  air-boxes  and 
brattice  act  with  sufficiency,  we  must  replace  these 
modes  of  ventilation  (purely  temporary)  by  other  more 
perfect  means,  and,  above  all,  not  employ  air-boxes  in 
order  to  drive  winning-places,  because  the  ventilation 


72  MINE   VENTILATION.  §  27. 

would  be  insufficient,  owing  to  the  length  which  would 
be  required ;  and  impure  air  would  injure  the  miner's 
health. 

Again :  should  an  explosion  take  place,  the  boxes 
would  be  destroyed,  ventilation  stopped,  and  the  after- 
damp would  spread  through  the  workings,  and  cut  off 
all  chance  of  escape  to  the  uninjured,  and  all  hope  of 
relief  to  the  injured.  As  soon  as  the  shaft  wins  the 
coal,  it  should  be  connected  with  a  neighboring  shaft, 
so  as  to  produce  a  regular  and  continuous  circulation 
of  air.  This  is  usually  effected  by  driving  two  ways, 
forming  a  single  conduit  with  two  sides  of  the  pit,  so 
that  the  air  must  pass  around  the  face  of  the  drift. 
Sometimes  a  single  drift  is  driven,  divided  by  a  brattice ; 
sometimes  two  parallel  drifts,  separated  by  a  wall  of 
coal,  cut  through  or  holed  at  equal  distances  by  cross- 
drifts  or  stentings,  which  are  afterwards  closed  up,  only 
leaving  the  one  nearest  the  face  open.  After  communi- 
cation is  made,  the  brattice  should  be  removed.  * 

MIXES  WITH  TWO  ORIFICES. 

27.  A  colliery,  which,  over  a  small  area,  has  many 
openings  to  the  day  of  great  sectional  area  but  of  little 
length,  requires  little  or  no  mechanical  ventilation. 
When  the  pits  are  less  numerous,  and  the  galleries  are 
longer,  we  should  exercise  great  care  in  the  distribution 


§  28.  MINE   VENTILATION.  73 

of  the  air-current.  Formerly  all  the  galleries  were 
united  so  as  to  form  one  long  and  sinuous  airway,  of 
which  each  extremity  emptied  into  the  atmosphere 
directly,  or  into  the  pits.  The  air  descended  one  of 
these,  traversing  its  whole  length,  and  finally  ascended 
the  upcast  shaft.  Places  were  stowed,  and  doors  erect- 
ed, so  as  to  direct  the  air-current  at  various  places.  The 
inconveniences  of  this  system  arose*  from  the  length  of 
the  air-course,  which  became  so  much  more  as  the  mine 
developed,  and  which  by  the  friction  diminished  the 
volume  of  air.  The  current  in  some  part  of  the  mine 
is  pretty  sure  to  meet  with  gases  of  some  nature  or 
other,  so  that,  if  they  be  mephitic,  the  air  will  pass  over 
the  workmen  in  the  return,  and  injure  their  health ; 
and,  if  the  air  has  acquired  sufficient  inflammable  gas, 
the  same  workmen  may  explode  it  with  their  lamps. 
In  two  collieries  alone,  where  this  system  of  ventilation 
was  adopted  (Lundhill  and  Risca),  three  hundred  and 
twenty-nine  lives  were  lost.  The  tendency  of  a  current 
of  air  is  naturally  to  choose,  in  passing  from  point  to 
point,  the  nearest  route,  and  that  which  has  the  largest 
section.  If  allowed  to  pursue  its  own  course,  the  air 
will  not  always  be  renewed  in  galleries  which  require  it. 

28.    To  overcome  this  difficulty,  doors  and  regulators 
are  employed ;  the  former  to  conduct  the  air  where  it 


74  MINE   VENTILATION.  §  2a 

is  needed,  the  latter  to  cause  a  diminution  of  the  vol- 
ume of  air  in  certain  portions  of  the  mine  where  only 
a  portion  of  the  current  is  needed.  Should  permanent 
stoppings  be  required  for  old  ways  or  abandoned  pas- 
sages, they  may  consist  of  solid  masonry,  tightly  stowed, 
so  as  to  leave  no  passage  for  a  single  thread  of  air :  en 
the  contrary,  they  must  be  movable  if  the  trams  and 
men  pass  along  the  gallery.  For  this  purpose,  recourse 
is  had  to  doors,  which  are  usually  placed  in  pairs,  but 
so  far  apart  that  one  may  be  shut  before  the  other  is 
opened.  Regulators  are  employed  to  prevent  more 
than  a  required  quantity  of  air  from  passing  into 
certain  districts,  and  to  cause  the  excess  to  pass  into 
other  parts  of  the  mine.  They  are  simply  sliding- 
doors,  whose  open  area  may  be  increased  or  diminished 
as  required  by  circumstances,  and  which  can  be  locked 
fast  at  any  area,  the  key,  of  course,  being  retained  by 
the  boss. 

(a)  To  illustrate  these  regulators,  let  us  assume  an 
airway  5'  X  5'  passing  10,000  cubic  feet  of  air  per  min- 
ute :  a  regulator  is  put  in,  which  contracts  it  to  20-foot 
area.  Find  the  quantity  of  air  that  will  pass,  power 
and  pressure  remaining  the  same. 

From  §  23,  5,  we  find  that  "  the  resistance  increases 
as  the  square  of  the  velocity  of  the  air-current,"  also 
we  know  that  sudden  contraction  of  an  airway  will 


§  28.  MINE   VENTILATION.  75 

cause  diminution  of  the  discharge;  then,  according  to 
§  23,  7,  we  have 

V^25  X  25  :  ^20  X  20  :  :  10000  :  7152  cubic  feet.     Am. 

(5)  As  we  have  regulated  the  discharge,  and  dimin- 
ished the  quantity,  we  may  increase  the  discharge  by 
enlarging  the  airway. 

Problem.  —  What  volume  of  air  Would  flow  through 
an  airway  10  feet  square,  when  6,000  cubic  feet  per 
minute  flow  through  an  airway  5  feet  square,  the  press- 
ure and  length  being  the  same  ? 


600°  <  *>  or  -  =  33840.     Ans. 

o:  V20  x  25 

In  the  above  case  the  area  was  enlarged  four  times. 
The  resulting  volume  would  have  been  increased  four 
times  also,  viz.,  24,000  cubic  feet,  had  it  not  been  that 
the  perimeter  only  increased  to  40  feet  instead  of  four 
times  its  former  size,  or  80  feet.  The  volume  may  be 
found  thus  :  — 

V/80  :  ^40  :  :  24000  :  33840  cubic  feet.     Ans. 


76  MINE  VENTILATION.  §29. 


CHAPTER  VIII. 

SPLITTING   THE  AIR-CURRENT.  —  BUBBLE'S   METHOD. 

29.  THE  splitting  of  the  air-current  of  a  mine,  when 
not  carried  to  extremes,  is  very  advantageous,  as  it 
secures  a  greater  volume  of  air  at  the  expense  of  the 
same  motive-power.  The  different  divisions  of  a  mine 
are  never  equally  developed;  and,  if  proper  care  be  not 
taken,  districts  requiring  the  most  air  will  receive  only 
a  small  portion,  while  other  districts  requiring  but  little 
will  receive  large  quantities.  Common  sense  suggests, 
that,  of  two  developed  districts  of  a  mine,  the  more 
developed  of  the  two  should  receive  the  larger  quantity 
of  air:  the  air  should  therefore  be  distributed  in  a  sys- 
tematic manner,  basing  the  quantities  for  each  district 
on  to  the  number  of  bends,  extent  of  rubbing-surface, 
and  other  resistances.  This  aim  is  attained,  as  men- 
tioned above,  by  the  "sliding  shutter,"  which,  being 
placed  so  as  to  admit  a  small  volume  of  air,  causes 
whatever  excess  there  may  be  to  pass  into  other  parts 
of  the  mine  where  the  air  is  more  needed. 

It  may  happen  that  a  u blower"  of  gas  is  met  with, 
which  renders  the  air  explosive  in  its  district.  When 
it  is  perceived,  the  regulators  should  be  immediately 


§  30.  MINE   VENTILATION.  77 

opened,  and  a  greater  circulation  produced,  in  order  to 
carry  away  the  inflammable  gas.  During  this  time 
work  in  the  other  districts  need  not  necessarily  be 
stopped,  unless  it  is  found  necessary  to  pass  the  whole 
current  through  the  dangerous  district. 

If  the  gases  be  given  off  in  such  quantities  that  an 
explosion  takes  place  before  the  miner  perceives  the 
explosive  state  of  the  air,  the  workmen  in  the  other 
districts  will  be  protected  from  the  flame  of  the  ex- 
plosion, and  the  "  after-damp "  will  only  momentarily 
check  the  current;  and,  if  the  return  airways  are  of 
large  sectional  area  and  no  great  length,  the  current 
will  scarcely  be  interrupted,  save,  perhaps,  in  the  dis- 
trict where  the  explosion  occurred,  the  doors  and  regu- 
lators of  which  have  been  destroyed.  Where  gas  is 
given  off  at  several  points  in  a  mine,  ventilated  by  a 
single  current,  the  aggregate  amount  may  be  suffi- 
cient to  render  the  current  explosive,  and  cause  an  ac- 
cident. 

30.  Either  to  increase  the  ventilating  pressure,  or  to 
lessen  the  extent  of  rubbing-surface  exposed  to  the  air 
circulating  in  mines,  is  a  very  slow  and  costly  manner 
of  increasing  the  amount  of  ventilation ;  but  by  judi- 
ciously dividing  the  current,  and  leading  it  into  several 
airways,  the  circulation  will  be  much  more  active  than 


78  MINE  VENTILATION.  §30. 

if  only  one  continuous  current  were  used.  Let  us,  as 
an  illustration,  assume  a  mine  divided  into  four  equally 
developed  districts  of  the  same  area  ;  and  also  the  same 
mine  arranged  so  as  to  form  one  continuous  airway, 
whose  length  will  be  four  times  greater  than  that  of 
one  of  the  districts.  Let  a  •=.  area,  p  =  perimeter, 
I  =  length,  and  Q  =.  quantity  of  air  circulating;  then 
we  have,  as  the  value  of  the  friction  of  the  air, 

plv*_pl      Q* 

—  v 

a         a      a* 

multiplied  by  a  co-efficient  to  be  determined  by  experi- 
ment. In  the  first  case,  the  airways  may  be  considered 
as  a  single  airway,  with  a  length  /,  a  section  4a,  and  a 
perimeter  4p  :  the  equation  then  becomes 


Secondly,  the  area  and  perimeter  being  a  and  /?,  the 
length  will  be  4Z,  whose  "  drag  "  or  resistances  due  to 
friction,  are  expressed  by 


On  dividing  equation  (a)  by  (b)  we  find  (b)  is  -^ 
of  equation  (a),  i.e.,  the  friction  of  (a)  is  ^  that  of 


§31.  MINE   VENTILATION.  79 

(b)  ;  or  we  may  say  "that  the  resistance  to  the  motion 
of  the  air  in  a  mine  requires  in  a  single  current  a 
motive-force  sixty-four  times  greater  than  when  the 
air  is  divided  into  four  currents  of  the  same  sectional 
area  and  aggregate  length. 

The  same  is  true  for  bends  and  contractions  that 
require  a  motive-force  equal  to  the -square  of  the  vol- 
ume of  air  circulating  in  each  district.  Thus,  in  the 

first  case,  the  volume  of  air  was  -^   the  motive-force 

4 

Q2 

required  to  overcome  this  resistance  m  X  ^ ;   m  being 

a  numerical  co-efficient  depending  upon  the  number  of 
bends  or  strictures. 

In  the  second  case,  the  volume  Q  must  be  multiplied 
by  a  co-efficient,  which,  owing  to  the  quadruple  length 
of  the  airway,  must  be  equal  to  the  sum  of  the  four 
co-efficients  of  each  district,  or  4m  Q\  a  value  sixty-four 
times  the  first. 

31.  By  splitting  the  air-current,  or  leading  it  off  from 
the  downcast  into  the  different  districts  to  be  venti- 
lated, we  have  two  decided  advantages  over  the  old 
method.  In  the  first  place,  we  obtain  purer  air  for  each 
district ;  for  each  split  takes  its  fresh  air  directly  from 
the  downcast. 


80  MINE   VENTILATION.  §31. 

In  the  next  place,  we  obtain  more  air  by  decreasing 
the  velocity.  As  the  friction  increases  as  the  square 
of  the  velocity,  we  lessen  the  friction  by  lessening  the 
velocity,  and  using  the  same  power :  we  also  decrease 
the  cost  of  ventilation  more  than  by  any  known  means 
as  yet.  Were  it  not  for  the  resistances  of  the  shafts, 
the  results  of  splitting  the  air  would  be  easily  calcu- 
lated. 

Problem.  —  To  show  the  effect  of  splitting,  without 
considering  the  shaft  resistances:  suppose  we  have  a 
mine  circulating  18,000  cubic  feet  per  minute,  and  that 
the  area  of  the  gallery  is  25  feet,  the  length  1,000  feet. 
What  amount  of  air  will  circulate  when  the  current  is 
split  into  two,  three,  four,  and  five  equal  divisions,  the 
pressure  remaining  constant? 

The  effect  of  splitting  into  two,  three,  four,  and  five 
equal  air-courses  will  be  to  double,  treble,  etc.,  the  areas 
without  altering  the  rubbing-surface,  because  the  area 
after  splitting  is  two,  three,  etc.,  times  that  of  the  ori- 
ginal airway,  although  the  rubbing-surface  remains  the 
same ;  and  as  the  quantity  may  be  found  by  the  formula 

(x)  9 

we  may  substitute  the  values  of  the  symbols,  and  find 
the  quantities  of  the  various  splits  under  consideration. 


§31.  MINE  VENTILATION.  81 

Since,  however,  in  the  above  formula,  p,  &,  and  s  remain 
constant,  and  a  varies,  we  may  simplify  the  work  by 
eliminating  them,  and  use  ^a  X  a  =  q,  which  corre- 
sponds to  one  of  our  former  laws ;  viz.,  "  that  the  rela- 
tive quantities  will  be  according  to  the  square  root  of 
the  area  multiplied  by  the  area,  and  then  multiplied  by 
the  original  quantity  flowing  through  the  mine."  The 
pressure  may  be  found  thus :  — 

ksv*      0.0217  X  20000  x  (0.72)2 
p=  -  -  =  —  -r^~  — —  =  8.999  pounds. 

•tt  ZO 

Using  now  formula  (x) 


9  x  50 
g=V  n.0000000217  x  20000  X    50  =  5091° 


9  x  75 
q  =  ^  0.0000000217  x  20000  X     75  =  93525 


9  x  100 
*  =  V  0.0000000217X20000  X  10°  =  1440°° 


9  X  125  X  125  =  200070. 


1.0000000217  X  20000 

The  question  may  be  worked,  without  reference  to 
the  actual  dimensions  of  the  areas  and  rubbing-surfaces, 
thus : — 


82  MINE  VENTILATION.  §31. 

V/T  X  1:^2  X  2::  18000:  50910 
V^T  X  1:^3  X  3::  1.8000:93528 
V^l  X  1  :  fi  X  4  ::  18000  :  144000 
VI  X  1  :  fi  X  5  ::  18000  :  200070. 

The  difference  between  the  two  calculations  is  owing 
to  the  treatment  of  the  decimals,  and  assuming  the 
pressure  more  than  it  really  is. 

(£>)  There  is  a  difference  between  splitting  the  air, 
and  adding  an  air-course  of  the  same  length  and  area. 
In  the  above  example  the  area  was  doubled  while  the 
length  remained  unchanged ;  but,  if  we  were  to  add  an 
air-course  of  the  same  length  and  area,  we  would  double 
the  rubbing-surface  and  the  area.  In  fact,  we  cannot 
call  such  an  arrangement  a  split ;  for,  if  both  received 
an  equal  volume  of  air,  they  would  both  have  the  same 
pressure ;  but  that  pressure  would  only  be  a  small  part 
of  what  it  was  in  the  above  example,  first  case,  on 
account  of  the  increased  area:  therefore,  instead  of 
increasing  the  quantity  of  air,  we  diminish  it. 

To  illustrate  this  let  a  =  25  feet,  s  —  24,000  feet  in 
an  airway  passing  15,000  cubic  feet  per  minute:  add 
an  airway  of  the  same  length  and  area,  what  quantity 
will  flow  through  each?  Ans.  22,900  cubic  feet. 

The  units  of  power  necessary  to  circulate  the  above 
quantity  may  be  found  by  multiplying  the  pressure  by 
the  quantity  of  air  circulating  per  minute. 


§31.  MINE   VENTILATION.  83 

Jesv*       ~  ~ 

(z)  u  =  —  x  Q  =  p  x  Q. 

With  an  additional  airway  of  the  same  length,  a  and 
s  will  be  doubled  ;  and,  as  the  velocity  decreases  as  the 
cube  root  of  the  power,  we  have  the  formula 


to  obtain  the  quantity  of  air  in  cubic  feet  circulating 
per  minute. 

(<?)  When  we  have  splits  of  different  lengths,  and 
wish  to  know  the  size  of  regulators  so  as  to  allow  the 
same  quantity  of  air  to  each  division,  we  may  find  them 
when  we  know  the  size  of  the  first  regulator. 

Problem.  —  Suppose  we  have  five  different  splits  in 
a  mine,  200,  300,  400,  700,  and  800  yards  long  respec- 
tively, and  the  regulator  placed  at  the  entrance  of  the 
200  yards'  airway  be  9  square  feet.  What  will  be 
the  area  of  the  other  regulators  so  as  to  allow  the  same 
quantity  of  air  to  each  split  ? 


V300-T-  V200  =  1-22404. 
y/400-f-  ^200  =  1.41421. 
y/TOO-j.  0200=  1.87083. 
V800  -h-  0^00  =  2.00000. 


84  MINE   VENTILATION.  §  31. 

This  gives  us  the  rate  at  which  the  friction  increases 
when  compared  with  the  first  regulator ;  and  hence,  if 
we  multiply  each  of  the  above  quotients  by  9  respec- 
tively, it  will  give  us  the  area  of  the  required  regula- 
tors, thus :  — 

1.22404  x  9  =  11.0' 
1.41421  x  9  =  12.7' 
1.87083  x  9  =  16.8' 
2.00000  X  9  =  18'. 

(d)  Again :  if  we  wish  to  divide  a  given  quantity  of 
air  so  that  it  will  be  distributed,  as  it  is  needed,  into 
unequal  quantities  in  different  divisions  of  the  mine, 
we  may  do  so  in  the  following  simple  manner. 

Problem.  —  Suppose  we  have  50,000  cubic  feet  of  air 
to  be  distributed  in  five  divisions,  each  to  obtain  respec- 
tively 15,000,  12,000,  10,000,  7,000,  and  6,000  cubic  feet 
per  minute,  to  travel  at  a  velocity  of  5  feet  per  second ; 
which  velocity  is  sufficient  to  render  any  discharge  of 
fire-damp  harmless,  unless  it  happens  to  be  a  very  excep- 
tional case. 

Taking  the  first  case  as  an  example,  15,000  cubic  feet 
to  be  distributed  at  a  velocity  of  5  feet  per  second, 

5'  x  60  —  300'  per  minute,  1^^°  =  50  feet  area,  and 

oOO 

y/50  =  7.07  feet,   size   of  the   regulator  necessary  for 


§  32.  MINE  VENTILATION.  85 

the  first  split.  Proceeding  in  the  same  manner,  the 
regulators  to  admit  the  above  quantities  of  air  may  be 
found. 

32.  Airways  are  seldom  of  the  same  area  in  the  same 
mine,  but  are  subject  to  the  same  pressure  in  ventila- 
tion ;  and,  as  each  airway  takes  up  its  part  of  the  press- 
ure to  overcome  the  resistances  which  the  air  encounters 
while  passing  through  it,  we  may  find  the  pressure 
necessary  to  overcome  the  resistances  of  the  whole  mine 
by  adding  the  several  pressures,  or  the  pressure  for  each 
airway,  together.  If  a  mine  be  ventilated  by  a  number 
of  airways  of  different  areas  and  lengths,  they  must  all 
be  considered  as  subject  to  one  common  pressure,  and 
the  quantity  of  air  passing  in  each  may  be  found  by  the 
formula, 


This  is  derived  from  the  formula  q  =  v  T-  X  «?  in  which 

*  ks 

k  and  p  are  common  factors  for  each  airway,  and  hence 
need  not  be  considered. 

Problem.  —  Suppose  we  have  three  airways,  A,  B, 
and  C.  A  has  an  area  of  30  square  feet,  and  a  rubbing- 
surface  of  66,000  feet.  B  has  an  area  of  36  square  feet, 


86  MINE   VENTILATION.  §  33. 

and  a  rubbing-surface  of  96,000  feet.  C  has  an  area  of 
25  square  feet,  and  a  rubbing-surface  of  40,000  feet. 
What  quantity  of  air  will  pass  along  each,  if  the  total 
quantity  passing  be  50,000  cubic  feet  per  minute  ? 

For  the  sake  of  brevity,  the  rubbing-surfaces  may  be 
reduced  to  the  lowest  whole  numbers,  and  still  remain 
in  the  same  proportion  to  each  other  by  dividing  by 
2,000;  then 

A  =  Vli  X  30  =  28.602 


x  36  =  31.176 
C  =  Vfj  X  25  =  27.950 
Total     .     .     .  87.728 

The  proportional  part  passing  in  each  airway  may 
now  be  found  from  the  simple  proportions :  — 

A  =  87.728  :  28.602  ::  50000  :  16301.5  cubic  feet. 
B  =  87.728  :  31.176  ::  50000  :  17768.5  cubic  feet. 
C  =  87.728  :  27.950  ::  50000  :  15930.0  cubic  feet. 

33.  Find  the  quantity  of  air  which  will  pass  through 
a  mine  of  the  dimensions  as  given  in  the  following  table, 
with  a  total  pressure  of  six  pounds  per  square  foot. 
In  this  case,  the  upcast  and  downcast  shafts  are  given. 
A,  B,  C,  and  D  are  splits,  subject  to  the  same  pressure. 
We  may  assume  any  quantity  of  air  we  please  —  say, 


§33. 


MINE   VENTILATION. 


87 


50,000  cubic  feet  —  to  pass  through  each  division,  and 
then  find  the  actual  quantity  which  will  pass  under 
six  pounds'  pressure. 

Before  we  can  do  this,  however,  we  must  calculate 
the  pressure  for  the  circulation  of  50,000  cubic  feet; 
then,  by  adding  the  several  pressures  together,  place 
them  in  proportion,  as  shown  in  column  vni.  of  the  table. 

TABLE  VI. 


i. 

II. 

in. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

•«; 

i£ 

8 

>i    ' 

£ 

p  >|Z*  * 

^^ 

1 

. 

S*    • 

§£o^ 

5  P     x 

o 

3 
00 

bo 

X 

*1^ 

^.s|« 

£=3^1 

^^S 

M'-i* 

N 

t 

a 

3 

,0 

3 

||| 

ii  * 

111 

a  "o     || 
SS    ex 

o  •« 

QQ 

* 

PI 

tf 

° 

* 

<5     °° 

Upcast    . 

9X8 

72 

34 

17000 

50000 

2.470 

1.78 

42400 

Downcast 

8X8 

64 

32 

16000 

•    • 

50000 

3.316 

2.40 

42400 

A    ... 

7X7 

49 

28 

42000 

74.848 

18115.51 

15412 

B    .    .    . 
C    .    .    . 

8X4 
5X6 

32 
30 

24 

22 

36000 
22000 

42.666 
49.543 

10326.5  1 

2.542 

1.82 

8737 
10146 

D    .     .     . 

5X5 

25 

20 

20000 

39.528 

9567    J 

8105 

Next,  by  the  use  of  the  formula  q  =  y  ^-  X  «,  we  may 
obtain  the  actual  quantities.      Columns  vi.  and  vn.  are 


88  MINE   VENTILATION.  §  34. 

obtained  as  shown  by  §  32.    The  pressure  passing  50,000 
cubic  feet,  we  find  aggregates  8.328  pounds ;  then 

V8.328  :  05 ::  50000  :  42400  cubic  feet 
the  actual  quantity,  as  is  shown  by  the  table. 


CHAPTER  IX. 

34.  As  yet  no  rule  has  been  established  as  to  the 
quantity  of  air  necessary  for  ventilating  mines  of  dif- 
ferent capacities:  consequently,  sometimes  as  much 
air  is  sent  into  a  mine  employing  two  hundred  persons 
as  there  is  into  one  in  which  twice  that  number  are 
constantly  engaged. 

Scientifically  ventilated  mines  contain  a  certain  allow- 
ance of  air  for  each  person  working  under  ground,  as 
well  as  for  each  light  and  horse ;  also  for  various  other 
purposes.  Some  persons  think  they  can  determine  in 
a  general  manner  the  volume  of  air  necessary  for  a  mine, 
basing  it  upon  the  following  single  element,  the  num- 
ber of  miners  employed,  and  giving  to  them  a  greater 
or  less  volume  of  air,  varying  with  the  presence  or 
absence  of  fire-damp.  Let  us  see  if  this  be  correct,  and, 
to  do  so,  assume  that  each  workingman,  exclusive  of 


§34.  MINE  VENTILATION.  89 

horses  and  lights,  requires  one  hundred  cubic  feet  per 
minute,  taking  as  examples  two  mines  equally  de- 
veloped, although,  by  reason  of  the  nature  of  the  coal- 
seam  and  the  mode  of  working,  the  tonnage  hewn  by 
each  man  may  be  different,  and  only  require  sixty  men 
in  the  first  mine,  whilst  the  second  requires  a  hundred 
and  fifty  men. 

The  first,  we  will  say,  is  from  necessity  wrought  in 
two  workings  6'  X  5'.  The  volume  per  man  being  100 
cubic  feet,  the  total  volume  required  is  6,000  cubic  feet 
per  minute,  which,  divided  by  the  area,  30  -(-  30  =  60 
square  feet,  gives  100  feet  per  minute  as  the  velocity  of 
the  air.  In  the  second  case,  one  airway  is  required  with 
an  area  of  8'  X  &  =  40  square  feet.  The  total  volume 
circulating  will  be  100  X  150  =  15,000.  cubic  feet  per 
minute,  and  the  velocity  will  be  377.5  feet  per  minute. 
The  first  velocity  will  be  insufficient  to  sweep  away  the 
gas,  and  prevent  the  heating  of  the  air ;  while  the  other 
is  too  great,  and  would  incommode  the  workmen.  Thus 
a  volume  of  air  exclusively  founded  on  the  number  of 
men  employed  is  incomplete.  The  extreme  limits  of 
velocity  —  which  largely  regulate  the  temperature,  and 
indirectly  the  capacity  of  the  air  for  water-vapor  —  must 
be  fixed.  To  do  this,  a  record  of  the  development  of 
the  working ;  the  method  of  working ;  the  nature  of  the 
seam ;  the  splits,  if  any,  or,  if  not,  the  main  current ;  and 


90  MINE   VENTILATION.  §  34. 

the  more  or  less  abundant  production  of  gases,  must 
be  kept,  as  it  is  impossible  to  fix  in  a  lump  otherwise 
the  volume  of  air  necessary  for  a  fiery  mine,  where  the 
evolution  varies  in  such  great  limits.  On  account  of 
the  great  complication  of  such  calculations,  no  general 
system  can  be  established.  "  It  appears,  under  the  cir- 
cumstances, to  be  indispensable  to  proceed  by  analogy, 
by  classing  mines  according  to  the  more  or  less  favora- 
ble conditions  for  ventilation  in  which  they  are  situated, 
and  to  form  groups,  to  the  members  of  which  a  single 
and  absolute  rule  can  be  applied." 

In  some  mines,  of  course,  more  air  is  required  than 
in  others ;  but,  for  sanitary  purposes  alone,  120  feet  per 
minute  is  quoted  as  the  minimum  for  each  man  and 
boy ;  but,  where  gas  is  given  off,  twice  that  amount 
should  be  allowed.  No  person  should  be  allowed  to 
work  in  a  stagnant  atmosphere,  while  the  working-places 
and  goaves  where  the  gases  congregate  should  have  a 
supply  of  air  large  enough  to  dilute  and  deprive  them  of 
their  power.  In  all  excavations  where  air  is  renewed, 
and  in  the  galleries  of  mines  in  particular,  carbonic-acid 
gas  is  continually  found  in  more  or  less  quantity.  The 
ventilation  should  be  sufficient  to  draw  it  constantly 
away,  and  to  keep  that  quantity  which  is  mixed  with 
the  air  beneath  that  limit  beyond  which  it  would  be- 
come injurious  to  the  workmen. 


§  34.  MINE   VENTILATION.  91 

Mr.  Richardson,  who  paid  a  great  deal  of  attention 
to  the  subject,  estimated  that  the  quantity  of  air  re- 
quired for  vital  chemical  purposes  for  each  person  was 
upwards  of  1,000  cubic  feet  per  hour.  Of  this,  84 
cubic  feet  were  for  the  breathing  of  each  person ;  62.8 
cubic  feet,  for  displacing  carbonic  acid ;  258.4  cubic 
feet,  for  diluting  nitrogen  ;  and  27  cubic  feet,  for  dis- 
placing perspiration.  In  addition,  59.3  cubic  feet  should 
be  allowed  for  the  combustion  of  each  light,  and  2585 
cubic  feet  for  one  horse.  This  is  not  considered  an 
extravagant  estimate ;  and  some  hold  that  it  is  not 
enough  for  diluting  all  the  gases,  nor  for  removing  the 
air  after  being  breathed. 

"  By  some  modes  of  ventilation,  there  are  contrivances 
for  enabling  the  men  to  breathe  over  and  over  again 
the  same  air,  and  so  accumulate  nuisances ;  and  this  is 
more  especially  the  case  in  mines  which  do  not  give 
off  fiery  gases."  Such  things,  however,  should  not  be 
tolerated  at  the  present  age  in  any  district.  There  is 
now  no  difficulty  in  providing  air  in  sufficient  quanti- 
ties to  dilute  the  gases  given  off  in  fiery  mines,  and  so 
render  them  harmless.  Where  the  furnace  is  used  for 
'ventilation,  it  has  been  calculated  that  the  cost  of  ven- 
tilating the  most  difficult  mines,  and  where  there  is  a 
large  escape  of  gas,  need  not  exceed  an  English  penny 
per  day  per  man,  a: id  not  half  so  much  ill  mines  where 


92  MINE  VENTILATION.  §  35. 

little  or  no  gas  is  given  off.  The  cost  of  fan-ventilation 
is  not  as  great  as  the  furnace,  although  the  first  cost 
is  larger.  As  before  stated,  enlargement  of  airways, 
and  judicious  division  of  the  current  into  several  splits 
(which  should  begin  as  near  as  possible  to  the  down- 
cast), will  bring  the  air  much  purer  and  cooler  to  the 
miners,  and  also  greatly  increase  the  ventilation. 

PREVENTION  OF  COLLIERY  EXPLOSIONS. 

35.  Much  has  been  written  and  said  upon  this  sub- 
ject, yet  every  now  and  then  the  public  is  startled  with 
news  of  a  recent  explosion  where  numbers  of  lives  have 
been  lost.  The  investigations  which  follow  are  not 
always  satisfactory,  either  to  the  families  of  the  de- 
ceased or  the  managers.  Instances  may  be  cited  where 
the  injured  have  received  the  blame  for  the  negli- 
gences of  either  the  manager  or  his  "  fire-boss." 

There  are  laws  in  some  of  the  States  which  require 
the  managers  to  allow  each  miner  a  certain  quantity  of 
air.1  Whenever  there  is  "  bad  air,"  the  miner  should 
inform  the  "  mine-boss,"  and,  in  case  the  evil  is  not 
speedily  remedied,  report  the  fact  to  the  "  mine-inspect- 
or." JMiners  should  not  neglect  to  do  this,  even  if  it" 
costs  them  "  their  job  ;  "  because  they  risk  the  lives  of 

1  See  Sect.  7,  Pennsylvania  Mine  Laws. 


§  35.  MINE   VENTILATION.  93 

their  fellow-miners  as  well  as  their  own ;  and,  in  case 
of  accident  through  any  neglect  on  their  part,  the 
law  will  hold  them  responsible.  The  first  preventive 
means  which  should  be  insisted  upon  is  a  really  effi- 
cient and  "  safe  safety-lamp."  Many  of  the  so-called 
safety-lamps  are  no  safety-lamps  at  all :  in  fact,  they 
are  apt  "to  lull  the  inexperienced  into  false  se- 
curity." Hundreds  of  miners  imagine,  that,  if  they 
have  a  safety-lamp,  they  can  work  with  impunity 
in  the  most  fiery  veins,  and  can  defy  almost  any 
risk.  "  We  all  know  how  dangerous  such  false  se- 
curity must  be,  and  how  treacherous  many  of  the 
lamps  have  proven  when  a  sudden  'blower'  of  gas 
has  been  struck.  Again :  many  of  the  lamps  can  be 
picked  by  an  ingenious  collier,  and  the  most  disastrous 
consequences  have  resulted  from  this  tampering  with 
so-called  safety-lamps.  Whatever  may  be  said  to  the 
contrary,  the  mining-world  still  wants  a  really  safe 
safety-lamp,  —  one  which,  while  giving  a  good  light,  will 
defy  all  tampering  by  the  collier,  and  resist  any  amount 
of  explosive  gas  with  which  it  may  come  in  contact. 
Until  we  have  this,  we  may  look  in  vain  for  any  appre- 
ciable decrease  in  the  number  of  explosions  in  our  fiery 
pits,  and  the  lives  of  our  colliers  will  be  more  or  less 
in  jeopardy." 

Another  provision,  which  should  be  enforced  under 


04  MINE   VENTILATION.  §  35. 

every  circumstance,  is  to  prohibit  the  use  of  gunpowder 
in  all  fiery,  bituminous  mines.  Shot-firing  has,  in  all 
probability,  to  answer  for  more  fatal  casualties  than 
some  are  inclined  to  ascribe  to  it.  This  does  not  happen 
so  much  in  anthracite  mines,  from  the  fact  that  there 
is  scarcely  any  dust  floating  in  the  air  when  compared 
with  bituminous  mines :  however,  we  are  not  sure  but 
that  it  may  apply  in  some  instances  even  to  them. 

It  is  certain  that  people  are  maimed  and  burned  by 
blasting,  at  distances  varying  from  ten  to  a  hundred 
and  eighty  yards,  when  there  is  no  fire-damp  present  to 
cause  such  destruction ;  then,  it  is  quite  clear  that  this 
results,  either  from  the  simple  force  and  flame  of  the 
shot  on  account  of  the  weight  of  the  charge,  or  from 
this  force  and  flame  assisted  by  the  rapid  combustion 
of  coal-dust  as  it  travels  on  its  course,  or  from  the  force 
and  flame  assisted  by  an  instantaneous  emission  of  gas, 
in  consequence  of  a  partial  vacuum  being  formed  by 
the  rushing  blast.  With  a  view  of  testing  these  assump- 
tions, careful  experiments  were  made,  a  description  of 
which  may  be  found  in  "  Colliery  Guardian,"  England, 
p.  13,  vol.  xxxii.,  the  summing-up  of  which  is  as  fol- 
lows :  — 

"  1.  The  flame  from  a  blown-out  shot,  unassisted  by 
gas  or  coal-dust,  does  not  travel  farther  than  five,  or, 
at  the  utmost,  ten  yards,  entailing  little  or  no  danger. 


§35.  MINE  VENTILATION.  95 

"2.  If  coal-dust  be  present,  even  in  a  comparatively 
damp  mine,  the  flame  may  not  travel  fifty  yards.  That 
in  a  dry  mine  of  a  high  temperature  this  distance  would 
be  greatly  exceeded ;  and  since  miners,  as  a  rule,  con- 
sider themselves  safe  at  from  fifteen  to  twenty  yards 
from  the  point  where  the  powder  is  used,  a  blown-out 
shot  under  these  circumstances  is  a  source  of  great 
danger. 

"  3.  That  the  violence  of  the  blast  from  either  gun- 
powder or  fire-damp  is  much  increased  when  coal-dust 
is  present. 

"  4.  That,  on  any  partial  vacuum  being  formed  in  an 
underground  coal- working,  fire-damp  will  instantly  issue 
in  dangerous  quantity ;  and  there  are  fairgrounds  for 
assuming  that  a  shot  blowing  out  in  the  face  of  a  nar- 
row heading,  and  setting  coal-dust  on  fire  in  its  course, 
would,  by  its  exhaustive  action,  produce  such  a  vacuum, 
and  might  cause  a  serious  explosion  in  a  mine  practi- 
cally clear  of  gas. 

"5.  Although  no  experiments  have  been  made  di- 
rectly to  test  the  result  of  coal-dust  set  on  fire  in  air 
heavily  loaded  with  fire-damp,  there  is  every  likelihood 
that  such  an  occurrence  would  be  attended  with  grave 
consequences. 

"  6.  That  it  is  desirable  that  any  system  of  blasting 
coal  which  entails  heavy  charges  of  gunpowder,  and  an 


96  MINE   VENTILATION.  §  36. 

unusual  liability  to  '  shots  blowing  out,'  such  as  blast- 
ing without  side-cutting,  or  nicking,  or  using  improper 
materials  for  stemming,  should  be  discontinued. 

"  7.  A  large  body  of  flame,  such  as  results  from  a  very 
heavy  charge  or  from  a  blown-out  shot,  is  required  to 
ignite  coal-dust;  that  in  blasting  with  charges  not 
exceeding  twelve  ounces,  accompanied  by  the  proper 
preparation  of  holing  and  side-cutting,  there  is  little 
liability  of  this  taking  place. 

"  To  discard  all  shot-firing  means,  in  many  mines,  a 
considerable  increased  cost  in  the  working  of  coal. 
But  life  is  the  first  consideration,  and  the  safety  of  the 
collier  should  be  the  one  great  object  of  the  proprietor 
and  manager.  The  opinion  of  the  best  mining  engi- 
neers is,  that  so  long  as  shot-firing  is  allowed,  even 
under  the  most  favorable  circumstances,  so  long  will 
there  be  a  certain  amount  of  risk,  while,  in  many  cases 
where  the  plan  is  adopted,  it  often  leads  to  most  seri- 
ous and  fatal  consequences." 

36.  The  third  point,  which  should  be  earnestly  con- 
sidered, is  efficient  ventilation.  There  is  no  country 
in  the  world  where  such  facilities  are  offered  for  good 
ventilation,  because  of  the  thick  coal-seams ;  yet  in  very 
many  instances  managers  appear  to  rely  too  much  upon 
this  advantage,  and  fail  to  conduct  the  air  properly  in 


§  37.  MINE  VENTILATION.  97 

its  journey  through  the  mines ;  and  there  are  some  that 
could  not,  although  by  law  required,  give  the  inspector 
a  design  of  their  ventilation.  Thus  it  is  not  at  all  to 
be  wondered  at,  when  such  gross  negligence  prevails, 
that  accidents  now  and  then  occur.  The  cheapest 
method  of  obtaining  more  air  is  by  splitting,  and 
mechanical  means. 

Enlarging  the  airways  lessens  the  velocity,  and  is 
another,  though  costlier,  mode  of  obtaining  more  air: 
in  small  seams  it  is,  however,  absolutely  imperative. 


CHAPTER  X. 

MEASUKING  THE   AIR. 

37.  To  measure  air  travelling  through  mines,  various 
methods  have  been  employed :  those  in  most  general 
use  may  be  classed  under  three  heads ;  viz.,  — 

(«)  Travelling  at  the  same  velocity  as  the  air-current, 
and  noting  the  distance  passed  over  in  a  unit  of  time. 

(5)  Determining  from  observation  the  rate  at  which 
small  floating  particles  are  carried  along  by  the  cur- 
rent, and  assuming  their  velocities  to  be  identical  with 
that  of  the  air-current  itself. 

(V)  By  the  use  of  the  anemometer,  or  other  instru- 
ments. 


98  MINE  VENTILATION.  §  37. 

(#)  By  the  first  method  it  is  necessary  to  select  as 
regular  an  airway  as  possible,  in  which  is  measured  a 
length  of  from  fifty  to  two  hundred  yards.  This  is 
traversed  in  the  same  direction  as  the  current,  a  candle 
being  held  in  the  hand,  whose  flame  must  be  kept  ver- 
tical. The  time  of  walking  the  distance,  which  is  the 
same  as  the  velocity  of  the  air,  is  measured  by  a  watch. 
The  mean  of  two  or  three  experiments  gives  a  rough 
estimate  of  the  velocity. 

(5)  By  light  bodies,  such  as  down  or  powder-smoke, 
and  noting  the  time  it  takes  for  the  particles  to  pass 
from  one  point  of  the  gallery  to  another.  Under  this 
head  may  be  classed  measurements  made  by  ammonia, 
sulphuric-ether,  etc.  To  measure  air  by  volatile  liquids, 
small  phials  containing  the  liquid  are  broken  at  a  cer- 
tain place  in  the  airway,  and  the  time  noted  that  it 
takes  to  pass  from  this  point  of  the  gallery  to  another, 
the  distance  between  the  two  having  been  previously 
ascertained. 

By  vapor-measurements  Mr.  Arnold  constantly  ob- 
tained the  same  results.  This  method,  so  simple  in 
practice,  is  more  exact  than  measuring  by  powder- 
smoke,  down,  or  other  light  substances.  Mr.  Arnold 
considers  it  to  be  less  subject  to  error  than  the  best 
anemometer  yet  invented. 

On  the  other  hand,  others  claim  that  —  the  sense  of 


§  37.  MINE   VENTILATION.  99 

smell  being  more  acute  in  one  person  than  in  another, 
and  different  for  the  same  persons  at  different  times  — 
it  is  impossible  to  measure  the  air  as  accurately  as  with 
an  instrument. 

Many  experiments  made  with  anemometers  show  a 
variation  in  their  co-efficient  at  different  velocities  of 
the  air-current.  M.  Guibal,  in  order  to  suppress  this 
source  of  error,  sought  an  approximate  velocity ;  then, 
by  using  the  co-efficient  thus  found,  he  made  new  ex- 
periments, which  would  give  the  true  co-efficients. 
Two  anemometers  are  required  to  do  this :  if  they 
agree,  the  measurement  is  correct ;  if  they  do  not,  one 
of  the  two  is  wrong,  and  it  is  then  necessary  to  ascer- 
tain which. 

(GI)  Miners  have  long  recognized  the  importance  of 
knowing  the  volume  of  air  for  all  pressures  of  the  atmos- 
phere :  hence  they  regularly  measure  the  air  traversing 
all  the  main  intakes  in  the  returns  and  at  certain 
points  in  the  various  districts.  Some  use  powder- 
smoke  ;  but  that  test  has  been  practically  superseded 
by  the  anemometer :  however,  whatever  method  is 
employed,  the  measurements  are,  or  should  be,  made  at 
certain  prescribed  times.  There  are  many  and  vari- 
ous instruments  for  measuring  the  velocity  of  the  air, 
among  which  may  be  mentioned  Devillez's,  Dickinson's, 
Briam's,  Robinson's,  Casella's,  and  Casartelli's  ane- 


100  MINE  VENTILATION.  §37. 

mometers.  Briam's  is  the  one  most  generally  used  in 
this  country,  and  is  a  modification  of  Robinson's  as 
originally  made  for  meteorological  use.  It  consists  of 
a  series  of  vanes,  which  revolve  by  the  action  of  wind. 
Each  revohition  is  transmitted  to  dials  by  means  of 
wheels  and  pinions.  These  instruments  are  made  of 
various  sizes,  from  four  to  twelve  inches.  The  dials  are 
six  in  number,  marked  for  feet,  hundredths,  thousandths, 
etc.  Whatever  instrument  is  used,  all  that  is  required 
to  ascertain  the  velocity  is  to  read  the  figures  on  the 
respective  dials  before  and  after  experiment,  then  to 
subtract  the  first  from  the  second ;  to  the  remainder  is 
added  a  value  corresponding  to  the  constant  friction, 
and  which  will  be  found  with  the  table  that  comes  with 
each  instrument. 

The  special  formula  is  of  the  form 

F  =  ar  +  u 

in  which  r  equals  the  number  of  revolutions  per  minute, 
a  equals  constant  proportional  to  the  number  of  linear 
feet  traversed  by  the  air  in  a  revolution,  and  u  repre- 
sents the  losses  due  to  friction. 

For  the  anemometer  generally  used  in  Pennsylvania, 
the  correction  is  about  thirty  feet  when  the  instrument 
is  new  and  clean ;  but  the  dirt  and  grit,  to  which  it  is 


§  38.  MINE   VENTILATION.  101 

more  or  less  exposed,  have,  no  doubt,  a  tendency  to 
increase  the  friction,  or  the  correction  in  time.  To  de- 
termine the  amount  of  correction  required,  the  instru- 
ment is  placed  on  a  whirling  table ;  the  anemometer 
is  whirled  around  by  the  table  revolving ;  the  velocity 
of  the  table  is  then  compared  with  the  indications  of 
the  anemometer. 

38.  The  method  of  procedure  in  Conducting  experi- 
ments to  find  the  useful  effect  of  fan-ventilation  varies 
materially  from  the  ordinary  method  of  ascertaining 
the  velocity  of  the  air,  because  the  revolutions  of  the 
fan,  the  indicated  power  of  the  engine,  water-gauge, 
etc.,  must  be  considered. 

The  air  is  measured  by  the  anemometer  in  the  ven- 
tilator-drift if  possible.  At  the  place  of  measurement, 
strings  or  wires  should  be  fixed  so  as  to  divide  the  drift 
into,  say,  ten  divisions  of  nearly  equal  area.  The  ane- 
mometer should  run  at  least  one  minute  in  each  divis- 
ion ;  one  minute  interval  should  be  taken  for  reading 
the  instrument,  and  moving  it  to  the  next  division. 
Simultaneously  with  the  air-measurement,  diagrams 
should  be  taken  from  the  engine  at  intervals  of  three 
or  five  minutes.  Each  diagram  should  be  accompanied 
with  an  observation  of  the  water-gauge,  and  the  num- 
ber of  strokes  per  minute  of  the  engine-piston.  The 


102  MINE  VENTILATION.  §  38. 

usual  working-speed  should  be  adopted  for  the  experi- 
ment, and  it  should  be  maintained  as  uniformly  as 
possible  throughout  the  trial.  After  completing  the 
drift-measurements,  a  second  air-measurement  should  be 
made,  either  in  the  intake  or  return  airways,  to  check, 
in  some  degree,  the  drift-measurement.  To  make  these 
check-measurements,  move  the  anemometer  uniformly 
over  the  whole  area  of  the  airway,  for,  say,  two  min- 
utes, repeating  the  observation  twice  to  avoid  error. 
During  these  check-measurements,  diagrams  of  engine, 
and  observations  of  speed  and  water-gauge,  should  be 
taken,  as  in  the  first  measurement. 

The  laws  of  Mariotte  and  Gay-Lussac  may  be  applied 
to  correct  the  volume  of  air  measured  in  the  intake  or 
return  airways  to  the  condition  of  the  ventilator-drift 
at  the  surface ;  namely,  for  pressure  and  temperature, 
as  follows :  — 

Problem.  —  Supposing  the  volume  of  air  measured 
at  the  intake  to  be  100,000  cubic  feet  per  minute,  the 
required  volume  which  it  would  occupy  in  the  ventila- 
tor-drift is  found  to  be  107,900  cubic  feet  with  the  fol- 
lowing conditions :  — 

Barometer.       Temperature. 

Ventilator-drift 30.30"  60°  F. 

Intake  airway 31.25"  37°  F. 

Neglecting   any  small   increase   of  volume   due   to 


§38.  MINE   VENTILATION.  103 

evolution  of  gas,  or  absorption  of  aqueous  vapor  in 
the  mine,  we  have  in  the  ventilator  drift, 

100000  x  81^  x  (CO* +461)  =  107900  cubic  feet 
30.30"  X  (37°  4-461) 

In  order  to  find  the  amount  of  work  which  is  ex 
pended  in  producing  ventilation,  and  what  amount  is- 
lost  in  overcoming  friction,  it  is  necessary  to  use  an 
indicator,  the  diagram  of  which  will  -give  us  the  effec- 
tive horse-power,  which  differs  from  the  nominal  or 
theoretical  horse-power. 

Problem.  —  Find  the  per  cent  of  power  used  by  a 
fan  with  the  following  data  :  — 

Area  of  piston  484  inches;  stroke  2  feet;  speed  60 
revolutions,  or  240  feet  of  piston  per  minute  ;  indicated 
effective  pressure  on  piston  20.89  pounds  per  square 
inch ;  then, 

484  X  240  x  20.89 

-  =  73.54  horse-power  engine. 
ooOUO 

The   air  in  fan-drift  measures  106,680  cubic  feet  per 
minute.    Water-gauge  in  fan-drift  measures  2.8".    Then 

106680  x  2.80  x  5.2 

— Q       A  —  =  4/.06  horse-power  m  the  air. 

ooUUU 

Therefore  the  per  cent  of  power  utilized  will  be 
73.54  :  47.06  ::  100  :  64  per  cent.     Ans. 


1 04  MINE  VENTILATION.  §  39. 

THE  BAROMETER. 

39.  It  is  supposed  that  Torricelli  derived  from  Gali- 
leo the  definite  conception  of  atmospheric  pressure. 
Pascal,  however,  was  first  to  state  that  the  mercurial 
column  decreased  in  length  as  we  ascend.  This  ex- 
periment was  for  the  first  time  performed  at  Cler- 
mont,  on  the  top  of  the  Puy  de  Dome,  Sept.  19,  1648. 
The  barometer  in  its  simplest  form  consists  of  a  tube, 
about  thirty-four  inches  long,  closed  at  the  top.  This 
tube  is  filled  with  mercury,  then  inverted  in  a  vessel 
containing  mercury.  The  atmospheric  pressure  on  the 
vessel  of  mercury  will  force  the  mercury  up  the  tube, 
or  let  it  sink,  according  as  that  pressure  is  greater  or 
less.  These  risings  and  fallings  are  measured  by  means 
of  a  scale.  As  mercury  expands  by  heating,  it  follows 
that  a  column  of  warm  mercury  exerts  less  pressure 
than  a  column  of  the  same  height  at  a  lower  tempera- 
ture. It  is  usual,  on  this  account,  to  reduce  the  actual 
height  of  the  column  to  the  height  of  a  column  of  mer- 
cury at  the  temperature  of  freezing  water,  which  would 
exert  the  same  pressure. 

The  formula  for  this  correction  is 

7*0  =  h  -hm(t-  32°), 
in  which  h  =  height  of  mercury  at  £°,  hQ  =  height  of 


§  39.  MINE   VENTILATION.  105 

mercury  at  freezing-point,  m  —  co-efficient  of  expansion 
of  mercury  per  degree  Fahrenheit  =  -ggVg-  =  0.0001001. 

When  very  exact  readings  are  required,  corrections 
must  be  made  for  expansion  of  the  scale  by  which  the 
height  of  the  mercurial  column  is  measured,  also  for 
capillarity. 

(a)  The  Aneroid  Barometer  is  a  thin  metallic  vessel 
partially  exhausted  of  air,  and  sealed :  consequently  it 
will  expand  or  diminish  in  size  as  the  atmosphere  is 
lighter  or  heavier.  This  change  in  size,  M.  Vidi  made 
use  of,  and  transmitted  the  movement  to  an  index. 
The  Aneroid  Barometer  is  a  very  convenient  instru- 
ment; as  it  is  round,  and  of  small  compass.  In  the 
second  geological  survey  of  Pennsylvania  it  was  used, 
to  a  great  extent,  for  determining  heights,  and  making 
contours,  in  the  anthracite  coal-regions.  Good  Aneroid 
Barometers  are  compensated  for  differences  of  tempera- 
ture. 

(5)  Atmospheric  pressure  will,  according  to  the  con- 
dition of  the  weather,  vary  from  28.5  to  31  inches  of 
mercurial  column.  When  the  barometer  rises,  the  ther- 
mometer usually  falls,  and  vice  versa.  The  discharge 
of  gas  becomes  greater  when  the  barometer  falls,  be- 
cause the  atmospheric  pressure  which  before  kept  the 
gas  pent  up  is  lessened ;  and  hence,  wherever  the  press- 
ure of  gas  is  strong  enough  to  overcome  the  lessened 


106  MINE   VENTILATION.  §  39. 

atmospheric  pressure,  it  escapes.  The  barometer  is 
useful,  therefore,  as  it  will  give  warning  when  an  in- 
creased discharge  of  gas  will  take  place ;  and  hence 
precautions  may  be  taken  to  overcome  it  by  increasing 
the  volume  of  air. 

Sudden  falling  of  the  barometer  is  much  more  dan- 
gerous than  a  gradual  fall ;  for  in  the  first  case  more 
gas  will  be  given  off  in  less  time  than  in  the  second. 
When  the  barometer  is  27  inches,  the  pressure  of  the 
atmosphere  per  square  foot  is  1,908.23  pounds ;  at  28 
inches,  it  is  1,978.90  pounds  ;  at  29  inches,  it  is  2,049.58 
pounds;  at  30  inches,  it  is  2,120.25  pounds;  at  31  inches, 
it  is  2,190.93  pounds. 

The  following  table  will  be  found  useful  in  order  to 
ascertain  the  pressure  per  square  foot,  or  fractional  part 
of  a  foot,  for  a  given  height  of  the  barometer. 


§39. 


MIKE   VENTILATION. 


107 


TABLE   VII. 
PRESSURE   OF   AIR  PER   SQUARE  FOOT. 


Inches. 

Pounds. 

Inches. 

Pounds. 

Inches. 

Pounds. 

0.01 

0.71 

0.12 

8.48 

0.50 

35.34 

0.02 

1.41 

0.13 

9.19 

0.60 

42.41 

0.03 

2.12 

0.14 

9.90 

0.70 

49.48 

0.04 

2.83 

0.15 

10.60 

0.80 

56.54 

0.05 

3.53 

0.16 

11.31 

0.90 

63.61 

0.06 

4.24 

0.17 

12.02 

.      1.00 

70.68 

0.07 

4.95 

0.18 

12.72 

2.00 

141.36 

0.08 

5.65 

0.19 

13.43 

3.00 

212.04 

0.09 

6.36 

0.20 

14.14 

4.00 

282.72 

0.10 

7.07 

0.30 

21.20 

0.11 

7.77 

0.40 

28.27 

Problem.  —  Require  the  amount,  in  cubic  feet,  of  air 
and  gas  that  may  be  expected  to  be  given  off  for  1,000 
cubic  feet  of  open  space  in  the  goaves,  or  other  waste 
places,  by  a  falling  of  the  barometer  from  30.4  inches 
to  28.75  inches. 

The  pressure  at  30.4    inches  =  2,148.52  pounds 
The  pressure  at  28.75  inches  =  2,031.91  pounds 


Then, 
or 


Difference 116.61  pounds. 

2,148.52  :  116.61  ::  1000  :  54.27, 
30.40  :  (30.40  -  28.75)  ::  1000  :  54.27 


108  MINE   VENTILATION.  §  39. 

cubic  feet  of  gas,  which,  theoretically,  may  be  given 
off  by  a  reduction  of  pressure  equal  to  that  indicated 
above. 

Experience  in  the  use  of  the  barometer  in  mines  has 
shown  that  its  indications  are  from  one  to  three  hours 
behind  what  is  actually  taking  place.  On  this  account 
it  has  been  asserted  that  the  barometer  is  not  to  be 
relied  upon  to  give  warnings.  According  to  the  "  Col- 
liery Guardian,"  Jan.  31,  1883,  the  government  issued 
and  sent  out  in  England,  during  the  year  1882,  thirty- 
two  warnings,  nineteen  of  which  were  justified  by  sub- 
sequent events.  Twelve  were  followed  in  three  days 
by  explosions  which  caused  one  hundred  and  thirty -nine 
deaths ;  two  were  followed  on  the  fifth  day  by  explosions 
causing  forty-three  deaths ;  twenty-three  lives  were  lost 
on  the  sixth  day  after  the  warning  —  showing  that  a 
total  of  two  hundred  and  five  lives  were  lost  in  six  days 
from  the  issue  of  the  warnings,  while  five  lives  were 
lost  on  the  day  of  the  issue. 

We  have  noticed,  when  there  have  been  explosions 
telegraphed  from  England,  that,  within  a  short  time, 
explosions  have  occurred  in  our  American  mines.  This 
warning  should  never  be  slighted,  whether  the  explos- 
ions are  due  to  falling  or  rising  barometer.  These 
teachings,  we  are  aware,  conflict  with  some  of  the  late 
writings  on  this  point;  but  we  are  so  convinced  by 


§  40.  MINE   VENTILATION.  109 

analogy  that  one  of  our  very  best  warnings  is  the  ba- 
rometer, that  we  hope  our  own  government  will  follow 
England's  Signal  Service  Bureau,  and  send  our  colliery 
managers  warnings. 


CHAPTER  XI. 

CONCLUSION. 

40.  THE  first  method  employed  to  ventilate  mines 
was,  we  believe,  to  agitate  the  air  by  shaking  a  cloth, 
next,  natural  ventilation  by  means  of  upcast  and  down- 
cast shafts.  This  method  was  followed  from  necessity 
by  the  furnace  ;  and  even  to-day  this  latter  method  is 
considered  by  some  the  best,  on  account  of  the  liability 
of  mechanical  ventilators  to  get  out  of  order,  and  so 
stop  the  current.  The  furnace  is  still  used  in  many 
mines,  but  is  being  gradually  superseded  by  the  me- 
chanical means  now  at  our  command.  It  is,  however, 
more  effective  in  deep  mines  than  any  thing  as  yet 
employed  ,  but  it  is  just  in  this  position  that  it  is  the 
most  dangerous,  as,  the  deeper  we  descend,  the  more 
gas  we  are  likely  to  encounter.  In  shallow  mines,  espe- 
cially if  worked  at  a  dip,  the  fan  is  the  more  economical 
of  the  two  systems.  The  steam-jet,  at  one  time,  was 


110  MINE   VENTILATION.  §  40. 

a  rival  of  the  furnace.  This  was  followed  by  allow- 
ing water  to  fall  down  the  downcast ;  but  this  system 
proved  inefficacious,  as  it  did  not  provide  enough  change 
of  temperature,  and  the  water  had  to  be  pumped  back 
again,  in  most  cases,  out  of  the  mine.  The  mechanical 
ventilators  of  late  years  have  been  numerous ;  but,  of 
all  the  number,  not  one  perfect  one  has  been  produced. 
Guibal's  Fan  seems  to  be  the  favorite;  and  to  him  is 
due  the  simplest,  and,  with  his  sliding  shutter,  the  most 
effective  fan.  Nixon  made  a  ventilator  on  the  air-pump 
system,  the  immense  piston  of  which  goes  backwards 
and  forwards  on  wheels.  The  air  is  received  into  a 
chamber,  and  forced  out  by  this  piston  :  it  works  ex- 
actly upon  the  same  principle  as  a  pump,  drawing 
the  air  from  the  mine  by  one  set  of  valves,  and  then 
forcing  it  out  by  another  on  the  back  movement  of  the 
piston. 

Mr.  Struve  constructed  a  machine  upon  a  principle 
similar  to  that  of  Mr.  Nixon,  using  two  large  gas-tanks, 
arranged  with  valves.  These  gasometers  moved  up 
and  down  alternately  in  water,  this  means  taking  the 
place  of  a  piston.  There  are  also  centrifugal  machines, 
receiving  the  air  at  the  centre,  and  throwing  it  off  from 
the  ends  of  the  blades :  others  are  made  on  the  wind- 
mill plan,  each  blade,  as  it  revolves,  cutting  out  a  defi- 
nite portion  of  the  air.  The  Champion  Ventilator, 


§  40.  MINE  VENTILATION.  Ill 

the  only  really  distinctive  American  ventilator,  is  so 
arranged  as  to  be  used  either  as  a  forcing  or  exhaust- 
ing fan.  It  is  credited  with  very  good  results.  Every 
new  fan  which  has  been  built  of  late  has  been  declared 
to  give  at  least  ten  per  cent  more  air  for  the  same 
amount  of  power  than  any  fan  previously  invented. 
This  can  hardly  be  believed,  unless  it  has  been  proven 
by  placing  the  new  fan  in  a  position  where  some  other 
fan  has  been,  with  the  conditions  of  the  mine  and  the 
power  just  the  same. 

Theoretical  comparison  of  two  fans  at  different  mines 
cannot  give  any  thing  like  exact  results,  as  the  air- 
ways and  resistances  will  not  be  similar  in  the  two 
mines ;  and,  while  one  fan  may  be  better  than  the  other, 
yet,  in  its  position,  it  may  be  unable  to  cope  with  an 
inferior  adversary  more  favorably  situated.  A  larger 
water-gauge  may  be  obtained  in  the  fan-house  than  in 
the  airway  leading  to  the  fan:  this  is  accounted  for 
by  the  fact  that  the  fan  offers  more  or  less  resistance  to 
the  air,  and  slightly  impedes  its  discharge.  A  perfect 
fan  should  not  do  this,  —  at  least  to  any  great  extent. 
Theoretically  and  practically  the  amount  of  ventilation 
obtainable  from  furnace-action  will  depend  upon  the 
difference  in  weight  of  two  air-columns.  An  improper 
consideration  of  this  subject  has  led  the  enemies  of 
the  furnace  to  state  that  there  is  a  material  difference 


112  MINE   VENTILATION.  §  41. 

between  the  action  of  furnace  and  fan  ventilation  ;  the 
former  being  likened  to  propulsion,  the  latter  to  trac- 
tion. Were  the  air  propelled,  the  power  expended 
would  be  applied  to  force  the  air  down  one  of  the 
shafts,  which  the  furnace  does  not  do,  but  draws  the 
air  down,  expelling  it  in  lighter  form,  the  same  as 
the  exhaust  fan. 

41.  Suppose  the  exhaustion  produced  in  a  fan-drift 
at  40  revolutions  per  minute  of  the  fan  averages  about 
1.25  inches  of  water-gauge,  while  at  60  revolutions  of 
the  fan  we  have  2.8  inches  water-gauge,  —  a  rise  propor- 
tional to  the  square  of  the  speed.  Since  the  vacuum 
increases  as  the  square  of  the  number  of  revolutions 
per  minute,  the  quantity  of  air  produced  should  be  the 
same  per  revolution  at  any  speed  where  the  conditions 
are  unchanged,  for  the  volume  of  air  varies  as  the 
square  root  of  the  water-gauge  ;  i.e.,  the  square  root 
of  the  lowest  pressure  bears  the  same  relation  to  the 
square  root  of  the  highest  pressure  as  forty  revolutions 
bear  to  sixty  revolutions  per  minute  ;  or 


Therefore,  if  it  were  desirable  to  pass  double  the  quan- 
tity of  air  though  a  mine  or  drift  where  the  existing 
friction  is  equal  to  one  inch  of  water-gauge,  without 


§41.  MINE  VENTILATION.  113 

making  any  alteration  in  the  underground  arrange- 
ments, the  effect  of  the  change  would  be  to  increase  the 
measure  of  resistance  to  four  inches  of  water-gauge; 
also  the  power  required  to  overcome  this  friction  would 
be  eight  times  that  employed  for  the  original  quantity, 
as,  in  addition  to  the  friction  being  fourfold,  the  volume 
of  air  is  also  doubled.  In  like  manner,  for  three  times 
the  quantity,  we  have  nine  times  the  resistance,  and 
require  twenty  seven  times  the  power. 

The  following  table  is  taken  from  Mr.  R.  Howe's 
paper,  printed  in  the  Transactions  of  Chesterfield  and 
Derbyshire  Institute  of  Engineers;  the  fan  under  con- 
sideration being  a  Guibal.  In  the  preparation  of  the 
table,  the  following  general  principles  are  observed :  — 

1st,  The  quantity  of  air  increases  in  proportion  to 
the  speed  of  the  fan. 

2d,  The  water-gauge  increases  proportionately  to  the 
square  of  the  number  of  revolutions  of  the  fan. 

3d,  The  horse-power  in  the  air  increases  as  the  cube 
of  the  quantity. 

4th,  The  steam  pressure  in  the  cylinder  is  in  propor- 
tion to  the  square  of  the  piston's  speed. 

5th,  The  horse-power  of  the  engine  is  proportionate 
to  the  cube  of  the  number  of  revolutions  per  minute, 
or  to  the  cube  of  the  volume  of  air. 

Illustrations :  — 


114  MINE  VENTILATION.  §  41. 

1st,      25  rev.  :  30  rev.  :  :  44450  :  53340  cubic  feet  of  air. 
2d,       (25)2rev.  :  (30)2rev.  :  :  0.48  w.g.  :  O.G9+  or  0.7  w.g. 

44450  x  0.48  x  5.2 

3d,  -  =  34  horse-power  in  the  air. 

ooOOO 

4th,      (25)2:  (30)2:  :  3.G2  :  5.21+  pressure  on  piston. 
5th,     (25)8:  (30)8:  :  5.32  :  9.19  effective  HP.  of  engine. 

Assuming  the  quantity  of  air  discharged  for  each 
revolution  of  the  fan  to  be  1,778  cubic  feet,  then,  at  25 
revolutions  per  minute,  the  number  of  cubic  feet  pass- 
ing will  be 

25  X  1778  =  44450  cubic  feet. 

This  does  not  always  hold  good  when  the  number  of 
revolutions  are  greatly  increased,  from  the  fact  that 
the  baffling  of  the  air  does  not  admit  the  water-gauge 
to  register  correctly.  "  The  theoretical  quantity  of  a 
fan  at  High  Colliery  was  short,  when  compared  with 
the  measurements,  3,048  cubic  feet  per  minute."  The 
fan  gave  off  1,584  cubic  feet  per  revolution:  there- 
fore the  quantity  that  should  have  been  delivered  was 
82,368  ;  but  from  measurement  81,923  cubic  feet  were 
delivered  at  1.3  inches  water-gauge.  From  the  formula 


it  was  found  that  while 


X  82.36  =  99.665  cubic  feet 

l.o 


§42. 


MINE   VENTILATION. 


115 


was  all  that  the  water-gauge  called  for,  the  measured 
quantity  was  102.713  cubic  feet,  making  a  difference  in 
the  second  case  of  3.048  cubic  feet  per  minute,  as  stated 
above. 

TABLE  YIII. 
GUIBAL  FAJST. 


II 

& 
| 

|| 

•3 

gll 

1 

O  go 

Ed 

Si 

»  s 

X 

~f  1 

"o 
u- 

ll 

P  O 

J:  S  *^ 

4>     • 

If 

8  1 

S£ 

~  s 

111 

is 

S  2  «  a 

JfcJ  co  P,O 

|| 

* 

° 

o-"0 

B 

W 

w 

25 

0.48 

44,450 

3.40 

3.62 

5.32 

30 

0.70 

53,340 

5.88 

5.22 

9.19 

35 

0.95 

62,230 

9.29 

7.11 

14.59 

40 

1.24 

71,120 

13.94 

9.28 

21.78 

45 

1.57 

80,110 

19.85 

11.75 

31.02 

50 

1.94 

88,900 

27.23 

14.50 

42.55 

55 

2.35 

97,790 

36.25 

17.55 

56.64 

60 

2.80 

106,680 

47.06 

20.89 

73.54 

65 

3.28 

115,570 

59.84 

24.51 

93.50 

70 

3.81 

124,460 

74.34 

28.43 

116.77 

75 

4.37 

133,350 

91.93 

32.64 

143.63 

80 

4.98 

142,240 

111.57 

37.13 

174.31 

85 

5.62 

151,130 

133.82 

41.93 

209.08 

90 

6.30 

160,020 

158.85 

47.00 

248.20 

95 

7.02 

168,910 

186.83 

52.37 

291.90 

300 

7.77 

177,800 

217.90 

58.03 

340.46 

42.    The  Guibal  Fan  belongs  to  that  class  of  ventila- 
tors called  centrifugal,  because  of  the  air  being  thrown 


116  MINE   VENTILATION.  §  42. 

off  at  the  tip  of  the  blade  tangent  to  the  circumference 
of  the  fan.  There  are  probably  more  of  these  fans  in 
use  than  of  any  other  kind :  seemingly  they  have  the 
precedence  among  the  best  mining  engineers,  maybe 
from  their  simplicity  of  construction,  or  from  their  non- 
liability to  get  out  of  order.  The  committee  of  the 
North  of  England  Institute,  appointed  to  determine 
the  useful  effect  of  different  fans,  reported :  — 

Per  cent  useful  effect. 

Struve 57.80 

Guibal 52.95 

Waddle 52.79 

Schiele 49.27 

Thus  placing  them  nearly  on  a  par  with  a  displacement 
machine  in  the  van.  Mr.  Howe,  in  his  experiments 
quoted  above,  places  the  useful  effect  of  the  Guibal  at 
about  sixty-four  per  cent.  The  fan  is  enclosed  in  a 
house,  the  air  being  discharged  through  a  chimney 
which  gradually  expands  towards  the  top.  That  there 
is  a  certain  amount  of  benefit  derived  from  this  chim- 
ney has  been  proved  by  experiment,  simply  because  by 
its  use  there  is  a  saving  in  final  velocity  by  the  oppor- 
tunity it  affords  the  air  for  expanding.  The  opening 
for  the  discharge  of  the  air  is  regulated  by  an  adjustable 
shutter.  To  find  the  most  advantageous  position  for 
this  shutter,  a  series  of  experiments  must  be  instituted. 


§42.  MINE   VENTILATION.  117 

First,  the  shutter  is  fixed  at  a  certain  point,  then  the 
amount  of  air  ascertained  by  measurement,  as  before 
explained ;  the  shutter  is  now  lowered  and  the  meas- 
urement again  taken ;  again  the  shutter  is  lowered  and 
the  measurement  taken.  If,  however,  in  the  last  posi- 
tion, a  less  amount  of  useful  effect  is  shown  than  in  the 
previous  position,  the  shutter  has  been  lowered  beyond 
its  most  useful  position,  and  must  be  returned  to  the 
second  position. 

The  position  of  the  shutter  depends  upon  the  speed 
at  which  the  fan  runs.  Should  the  shutter  vibrate 
when  the  speed  is  increased,  it  shows  that  the  fan  is 
not  working  properly,  and  that  the  shutter  needs  regu- 
lating. 

A  modification  of  the  Guibal  Fan  is  used  in  the  an- 
thracite regions,  having,  instead  of  the  shutter,  a  spiral 
casing,  commencing  at  the  orifice  of  discharge  (throat), 
and  extending  sometimes  the  whole  .circumference,  ac- 
cording to  the  notion  of  the  engineer.  Whenever  this 
spiral  casing  is  too  short,  thumping  will  take  place. 
The  discharge  is  regulated  at  the  throat  by  a  short 
shutter,  or  by  nailing  boards  over  the  orifice.  The 
more  recently  built  fans  are  made  as  large  as  forty-five 
diameter,  and  have  fire-proof  casings  of  iron. 


118  MINE   VENTILATION.  §  43. 

COMPARATIVE  ECONOMY  OF  FURNACE  AND  FAN 
VENTILATION. 

(FROM  MB.  R.  HOWE'S  PAPER.) 

43.  Suppose  we  have  two  furnace-pits,  the  first  260 
feet  deep,  the  second  655  feet  deep. 

To  arrive  at  the  horse-power  of  furnace-ventilation, 
we  must  find  the  pressure  producing  it. 

First,  Barometer  of  the  first  pit,  30.3" ;  temperature 
of  downcast,  55?  ;  of  upcast,  240°.  The  pressure,  there- 
fore, of  the  downcast  in  pounds  per  square  foot,  is 

1.3253  x  30.3       26Q  =  2()  312          dg> 

459  +  55 

The  pressure  of  the  upcast  is 
1.3253  X  30.3 


459  -f  240 


X  260  =  14.936  pounds. 


20.312  —  14.936  =  5.376  pounds  as  the  pressure  per 
square  foot  for  ventilating  pressure,  and  this  pressure 
will  give  us,  say,  30,358  cubic  feet  of  air,  then  the 
horse-power  will  be 

30358  x  5.376 

-  =  4.94  horse-power  in  the  air. 

ooUUU 

Second,  Mean  barometer,  30.6";  temperature  of  down- 


§43.  MINE   VENTILATION.  119 

cast,  58°;  temperature  of  upcast,  117°;  then  the  press- 
ure in  pounds  per  square  foot  is,  for  downcast, 

1.3253  X  30.6       655  =  pounds ; 

459  +  58 

for  upcast, 

1.3253  X  30.6 


459  +  117 


X  655  =  46.116  pounds. 


Hence,  for  ventilating  pressure,  51.379  —  46.116  =  5.263 
pounds  per  square  foot ;  and  this  pressure  gives  48,230 
cubic  feet  of  air  |>er  minute,  which,  reduced,  gives  us 
7.69  as  the  horse-power  in  the  air. 

These  two  furnaces  ventilated  the  Hollingwood  pits. 
The  No.  1  furnace  used  3  tons  12  hundred  weight  of 
coal  in  24  hours,  or  68  pounds  per  hour  per  horse-power 
in  the  air.  No.  2  furnace  used  3  tons  1  hundred  weight 
per  day,  or  37  pounds  of  coal  per  hour  per  horse-power 
in  the  air.  The  two  furnaces  circulated  78,588  cubic 
feet  of  air,  with  a  horse-power  of  12.63. 

A  Guibal  Fan  was  afterwards  substituted  to  take  the 
place  of  these  furnaces,  the  ordinary  speed  of  which 
was  sixty  revolutions  per  minute.  The  average  quan- 
tity of  air  circulated  at  this  speed  was  106,680  cubic 
feet;  the  pressure,  2.8  water-gauge,  or  14.56  pounds  per 
square  foot. 


120 


MINE   VENTILATION. 


43. 


Tabulated  results  of  the  above  calculations  show  the 
economy  of  fan  over  furnace  ventilation.  The  wages 
and  price  of  coal  are  those  regulated  by  the  English 
market  at  the  time  of  the  writing,  reduced  to  United- 
States  money. 

TABLE  IX. 


li 

O1*" 

8*1 

*j    00    S 

*Js 

£»3  9 
Soft 

pi 

DUE  TO  FAN. 

cp 

Decrease. 

1.  Cubic  feet  of  air  per  minute  . 
2.  Pressure     in     pounds     per 
square  foot  

78,588 
5.304 
12.63 
$10.44 

$0.82 

49 

106,680 
14.56 
47.06 
$5.33 
$0.12 

10 

28,092 
9.256 
34.43 

$5.11 
$0.70 

39 

3.  Horse-power     in     air,     in- 
cluding shaft  friction     .     . 
4.  Cost  of  fuel,  wages,  etc.,  for 

5.  Cost  for  24  hours  per  horse- 
power in  the  air   .... 
6.  Pounds    of    coal  consumed 
per  horse-power  in  the  air 
per  hour  

Amount  saved  in  one  year  by  fan 

.     .     .     .     $2,120. 

65 

APPENDICES. 


APPENDIX.  A. 

FORMULAS.* 

44.    Let  a  =  area  of  airway  in  square  feet. 

0  =  perimeter  of  airway  in  feet. 

1  =  length  of  airway. 

s  =  rubbing-surface  in  feet. 

k  =  co-efficient  of   friction,  0.0217  of  a  pound 
at  a  velocity  of  1,000  feet  per  minute. 

p  =  pressure  in  pounds  per  square  foot  of  sec- 
tional area. 

v  —  velocity  of  the  air  in  feet  per  minute. 

w  =  water-gauge. 

q  =  quantity  of  air  circulating,  in  cubic  feet,  per 
minute. 

u  =  units  of  work  applied  to  circulate  the  air. 
HP  =  horse- power  of  ventilation. 

*  From  Mining  Herald  Almanac. 


122  MINE   VENTILATION.  §44. 

Then  the  following  formulas  for  friction  of  air  in 
mines  may  be  deduced :  — 

ksv2      pa      ksv~q      ksv3        u        q          q 
p         p          u          pv       pv      v  ~      i~^' 

k3/ 


A      8  -i0-_^___ 

~  kv'2~  kv8~  kv*~~  kv* 

.       pa       u        p       iv5.2 

v.       K   ==  • — ->  ^=  — z  =  — T)  ==  5 — • 

sv2      sv*      sv2        sv2 


a          a 


ksv2      u      pa      ksv*       u 

6.    p  = =  -=£-= =  —  =  5.2w. 

a         q       a          q         av 


rj          ..    a    *  •y  *<y  ic    »  y  F 

~pa~a~\ks~\ks  ~~  V  ks' 
ksv2 


\na  t 

9.     a  =  va  =  -  = =  ~-  X  a  =       ~  X  a- 

p        p         ks 

10.     u  =  qp  =  vpa  =  -  —  =  A:sv8  =  ^5.2^  =  HP 


X  33000. 


§44.  MINE   VENTILATION.  123 

U  qp 


11.      HP  = 


33000       33000 


12.  ^=^  =  fty^u 


,     ,       /      u\*      .        u 

14.    pa  =  Jcsv2  =  ( t8/ 7-  )   X  ks  =  — 

VV  ksj  v 

"  These  formulas  comprise  the  pressure  due  to  resist- 
ance, and  not  that  necessary  for  final  velocity:  they 
are,  therefore,  more  correct  for  long  than  for  short  air- 
ways. The  pressure  required  for  final  velocity  becomes 
a  smaller  fraction  of  the  whole  drag  as  the  airways 
extend.  If  it  be  required  to  take  into  account  the 
pressure  to  create  velocity, 

A*9?)^  7c^fi) 

Instead  of  using  a  =  -— ,  use =5. 

p  p-P 

Instead  of  using  pa  =  fcsv2,  use  a(p  —  P)  =  Jcsv*. 

ksv2  ksv*       JCSV* 

Instead  of  using  p  — ,  use  p  —  P  = ,  or f-  P. 

a  a  a 

Instead  of  using  s  =  J^,    use        7.^2       ' 

4  fpv         4  /(P  —  P)a 
Instead  of  using  v  =y  -JT-,  use  y  -  — ^ • 


124  MINE   VENTILATION.  §45. 

APPENDIX  B. 

PKOBLEMS. 

45.   1.   What  is  the  area  of  an  airway  6  feet  by  5  feet? 
What  is  its  perimeter  ?  a  —  30 ;  o  =  22.     Ans. 

2.  What  is  the  area  of  a  shaft  14  feet  diameter? 
Rule.  —  Diameter2  X  0.7854.        153.98  +  feet.     Ans. 

3.  What  is  the  perimeter  of  a  shaft  16.5  feet  diameter  ? 
Rule.  —  Diameter  X  3.1416.  58.83  +  feet.     Ans. 

4.  The  long  axis  of  an  elliptical  shaft  is  14  feet,  its 
short  axis  6  feet :  what  is  its  area  ? 

Rule.  — A  XaX  0.7854.  65.9736  feet.     Ans. 

5.  Find  the  perimeter  of  an  elliptical  shaft  whose 
axis  A  is  16  feet,  and  its  axis  a  8  feet. 

A  -\-a 

Rule.-  ~    2 —  X  3.1416. 

38.7  feet.    Ans. 

6.  An  air-course  is  500  yards  long,  6  feet  high,  and 
7  feet  wide :   what  is  its  area,  perimeter,  and  rubbing- 
surface  ? 

a  =  42  ;  o  =  26  ;  s  =  39000  square  feet.     Ans. 

7.  What   is   the   rubbing-surface  of  a  shaft  15  feet 
diameter,  1,200  feet  deep  ?  56548.8  feet.     Ans. 


§45.  MINE  VENTILATION.  125 

8.  In  an  airway  8  feet  by  9  feet,  when  the  current 
has  a  velocity  of  15  feet  per  second,  what  quantity  of 
air  is  passing  per  minute  ? 

Rule.  —  aXvX  60".  64800  cubic  feet.     Ans. 

9.  When  the  water-gauge  is  1.85  of  an  inch,  what 
pressure  per  square  foot  does  it  indicate  ? 

Rule.  —  w  X  5.2.  9.62  pounds.     Ans. 

10.  When  the  quantity  of  air  passing  is  60,000  cubic 
feet,  with  a  water-gauge  of  1.5  inches,  what  are  the  units 
of  work  producing  ventilation  ? 

Rule.  —  u=pq.  468000  units.     Ans. 

11.  What  horse-power  is  there  in  468,000  units  of 
work? 

14.18.     Ans. 


12.  The  pressure  producing  ventilation  is  7.8  pounds  : 
what  is  the  water-gauge  ? 

P 
Rule.  —  w  =  -/-$•  1.5  inch.     Ans. 

O.ju 

13.  There  are  50,000  cubic  feet  of  air  passing,  having 
a  rubbing-surface  24,000  feet,  and  an  area  of  20  square 
feet  :  what  is  the  water-gauge  ? 

ksv2 

Rule.  —  w  =  -^—.        3.12  inches  water-gauge*    Ans. 
5.2 


126  MINE   VENTILATION.  §45. 

14.  The  rubbing-surface  of  an  airway  is  25,000  feet, 
its  area  25  square  feet  :  what  is  its  length  ? 

1250  feet.     Ans. 

15.  What  units  of  work  are  necessary  to  overcome 
friction  of  an  airway  6  feet  by  6  feet,  1,000  feet  long, 
when  the  quantity  passing  is  7,200  feet  per  minute  ? 


v/ 


Rule.  —  u  =  —  -  X  <?•  4166  units.     Ans. 

a 

16.  Let  a  =  36  ;    *  =  24,000,   to   find  the   value   of 

=  1.39.    Ans. 

a 

17.  With  0.9  of  an  inch  water-gauge,  16,000  cubic 
feet  of  air  are  passing  :  what  quantity  will  pass  when 
there  is  a  water-gauge  of  1.6  inches  ? 

V^9  :  vT6  :  :  16000  :  21333  +.     Ans. 

18.  With  a  fan  and  furnace  combined,  46,706  cubic 
feet  are  produced  ;  the  furnace  produces  alone  4^,670 
cubic  feet:  what  will  the  fan  produce  by  itself? 

V467062  -  426702  =  18993.     Ans. 

19.  If,  with  a  water-gauge  of  0.65  of  an  inch,  20,000 
cubic  feet  of  air  are  obtained,  what    height  will  the 
water-gauge   be   when   there  is  a  quantity  of   75,000 
cubic  feet  of  air  passing  ? 

^  =  x  .-.  x2  X  w  =  9.139.     Ans. 


§45.  MINE   VENTILATION.  127 

20.  How  much  must  we  increase   the   pressure   to 
double  the  quantity  of  air?  4  times.     Am. 

21.  How  much  has  the  ventilating  power  to  be  in- 
creased to  treble  the  quantity  of  air  ? 

33  =  27  times.     Ans. 

22.  If  we  obtain  25,000  cubic  feet  of  air  by  5-horse 
power,  what  horse-power  "will  be  required  to  circulate 
60,000  cubic  feet  in  the  same  mine  ? 


or    qr  :  q  :  :  V5  :  \  Ans. 

23.  There  are  two  air-courses  through  which  a  total 
quantity  of  100,000  cubic  feet  of  air  is  passing;  the 
resistances  of  the  airways  are  in  the  proportion  of  4 
to  1  :  what  quantity  will  pass  along  each? 

V^l  X  100000       100000 

,-   .     /-  —  ==  —  3  —  —  33333^  cubic  feet  for  airway 

having  greater  resistance. 

\ll  x'looooo 

—  666661  cubic  feet  for  airway  having 

only  one-fourth  the  resistance. 

24.  Find  the  motive-column  where  the  upcast  and 
downcast  shafts  are  540  feet  deep,  the  temperature  of 
the  upcast  being  129°,  and  that  of  the  downcast  43°. 

JOQ  _  43 
Rule.  —  M=DX  459   .  43'  92-51-     Ans- 


128  MINE  VENTILATION.  §46 


APPENDIX   C. 

46.  THE  quantity  of  air  required  per  man  for  res- 
piration has  been  variously  estimated  by  the  following 
authorities :  — 

"  The  volume  of  air  contained  in  the  lungs,  accord- 
ingly is  109  cubic  inches ;  after  respiration,  60  cubic 
inches  remain  in  the  chest ;  total  volume  170  cubic 
inches.  Amount  of  each  inspiration  has  been  differently 
estimated,  it  is  probably  16  to  20  cubic  inches."  —  ME. 
GOODWIN. 

"Men  between  five  and  six  feet  in  height,  after  a 
complete. inspiration,  expel  by  force,  on  an  average,  225 
cubic  inches  at  60°.  This  is  called  'vital  capacity  of 
the  lungs.' '  -  MR.  HUTCHINSON. 

"  Assuming  a  man  takes  twenty  breaths  per  minute, 
each  40  cubic  inches  vitiates  28  cubic  feet  per  hour. 
Besides  this,  a  quantity  of  vapor  is  emitted,  which, 
according  to  Dumas,  amounts  to  0.0836  of  a  pound  of 
water  per  hour,  —  enough  to  saturate  7.1  pounds  of  air 
at  60°.  And  if  we  allow,  that,  to  be  healthful  and  pleas- 
ant, the  air  should  be  only  one-half  saturated,  we  require 
14.2  pounds  of  air,  or  187  cubic  feet,  giving  us  a  total  of 
215  cubic  feet  per  hour,  which  happens  to  be  the  capa- 
city of  a  6-foot  cube.  This  is  the  maximum  quantity 


§46.  MINE  VENTILATION.  129 

necessary  for  clean,  healthy  persons.  For  prisons^  etc., 
it  should  not  be  less  than  350  cubic  feet,  and  for  hospi- 
tals 1,000  cubic  feet,  per  hour  per  head."  -  -  MR.  Box. 

"  A  minimum  of  100  cubic  feet  per  minute  for  each 
man  and  boy,  for  sanitary  purposes  alone."  —  MR.  HER- 
BERT MACKWORTH. 

"From  100  to  500  cubic  feet  per  minute  for  each 
collier,  according  to  condition  of  the  mine."  —  MR. 
HEDLEY. 

"The  minimum  quantity  of  fresh  air  for  the  most 
harmless  of  pits  ought  to  be  from  10,000  to  15,000 
cubic  feet  per  minute."  —  MR.  DUNN. 

"  In  most  fiery  mines,  an  average  of  600  cubic  feet 
per  minute  per  collier  is  circulated,  and  nearly  200  cubic 
feet  per  minute  for  each  acre  of  waste."  —  PROFESSOR 
PHILLIPS. 

"  For  all  anthracite  mines,  nearly  double  the  above 
estimates  (which  are  for  bituminous  mines)  should  be 
allowed,  because  of  the  much  greater  volume  of  powder- 
smoke,  due  to  the  large  amount  of  blasting  done."  — 
THOMAS  J.  FOSTER. 

The  Mine  Ventilation  Act  for  the  anthracite  region 
of  Pennsylvania  provides  for  66  cubic  feet  of  pure  air 
per  minute  for  each  man  working.  All  authorities 
agree  in  declaring  this  amount  inadequate. 


130 


MINE   VENTILATION. 


§47. 


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APPENDIX  D. 

ASPHYXIA. 

47.  THE  miners  are  exposed  to  asphyxia  when  the 
circulation  of  the  air  is  not  sufficiently  active,  and 
when  they  imprudently  penetrate  into  ancient  and 
abandoned  workings,  or  wherever  the  air  has  not  suffi- 
cient oxygen. 

The  symptoms  of  asphyxia  are  sudden  cessation  of 
the  respiration,  of  the  pulsations  of  the  heart,  and  of  the 
action  of  the  senses.  The  face  is  swollen  and  flushed; 


§  47.  MINE   VENTILATION.  131 

the  eyes  protrude ;  the  features  are  distorted,  and  the 
face  often  livid,  etc. 

It  is  necessary  to  succor  an  asphyxiated  person  with 
the  greatest  promptitude,  and  to  continue  the  remedies 
as  long  as  there  is  not  a  certainty  of  death.  The  best 
and  first  remedy  to  employ,  and  in  which  the  greatest 
confidence  has  been  and  should  be  placed,  is  the  re- 
newal of  the  air  necessary  for  respiration.  As  an 
instance,  let  me  cite  the  experience  jof  John  Boyle  and 
his  son  at  Yorktown,  Penn.,  who  were  as  near  death  as 
men  could  be,  and  return  to  life.  The  men  knew  the 
air  was  bad  in  their  place  (a  pitching-breast)  ;  but  the 
necessities  of  life  were  superior  to  their  discretion,  and 
they  continued  working  until  eleven  A.M.,  when  the 
young  man  concluded  he  could  stand  it  no  longer,  and, 
in  making  his  way  from  the  face  to  the  manway,  was 
overcome,  and  fell  ere  he  reached  it.  Mr.  Boyle,  who 
was  also  very  weak,  took  hold  of  the  boy,  arid,  between 
pulling  and  lifting  him  over  bowlders,  succeeded,  very 
luckily,  in  reaching  the  manway ;  but  there  he  found 
the  air  was  still  too  heavy  to  support  life.  The  exertion 
and  excitement  in  his  endeavor  to  rescue  his  boy,  and 
take  him  down  the  narrow  outlet,  together  with  the 
deadly  gas,  proved  too  much  for  him,  and  he.  too, 
fainted  away,  with  the  young  man  in  his  arms,  both 
becoming  tangled  fast  between  the  timbers,  foot-sills, 


132  MINE   VENTILATION.  §47. 

and  slabbing.  At  five  o'clock  in  the  afternoon,  a  com- 
pany hand  thought  something  was  wrong  because  of 
the  Boyles  remaining  in  the  breast  so  long,  without 
coming  down,  and  started  up  the  manway  after  them, 
and  found  them  near  the  top,  fast,  and,  as  he  thought, 
dead.  Aid  was  summoned,  and  the  miners  taken  down. 
The  young  man  revived  after  reaching  the  gangway. 
The  father  was  taken  home  on  a  stretcher,  and,  with 
much  care  and  labor,  was  brought  back  to  life.  This 
was  a  peculiar  case.  Had  there  been  a  larger  quantity 
of  black-damp  in  the  air,  neither  men  would  have  sur- 
vived; but  there  seems  to  have  been  enough  oxygen 
present  to  keep  life  in  their  bodies,  while  there  was  not 
enough  to  allow  of  their  keeping  their  senses. 

While  it  is  well  enough  to  know  the  following  meth- 
ods for  restoring  asphyxiated  persons,  and  to  employ 
them  while  waiting  for  the  doctor,  yet  it  is  imperative 
that  a  physician  be  summoned  immediately. 

The  following  short  and  clear  instructions  for  the 
recovery  of  suffocated  persons  are  those  issued  by  Napo- 
leon, 1813,  Tit.  iii.  Art.  xv. 

1.  Remove  the  patient  to  pure  air. 

2.  Undress,  and  bathe  his  body  with  cold  water,  par- 
ticularly about  the  neck. 

3.  Endeavor  to  make  him  swallow,  if  it  be  possible, 
cold  water  acidulated  with  vinegar. 


§47.  MINE   VENTILATION.  133 

4.  Clysters  should  be  given,  two-thirds  of  cold  water 
and  one-third  of  vinegar,  to  be  followed  with  others,  of 
a  strong  solution  of  common  salt,  or  senna  and  epsom 
salts. 

5.  Attempts  should  be  made  to  irritate  the  pituitary 
membrane  with  the  feather-end  of  a  quill,  which  should 
be  gently  moved  in  the  nostrils  of  the  patient ;  or  stimu- 
late it  with  ammonia  placed  under  the  nose. 

6.  Introduce  air  into  the  lungs  .by  blowing  with  the 
nozzle  of  a  bellows  into  one  of  the  nostrils,  compress- 
ing the  other  with  the  fingers. 

7.  If  these  means  do  not  produce  the  effects  expected, 
the  body  of  the  asphyxiated  person  remaining  warm 
(as  that  generally  occurs  for  a  long  time),  it  will  be 
necessary  to  have  recourse  to  blood-letting,  the  neces- 
sity of  which  is  indicated  by  the  redness  of  the  face, 
the  swollen  lips,  and  protruding  eyes.     The  blood  may 
be  taken  from  the  jugular  vein  or  foot. 

8.  As  a  last  resource,  an  opening  should  be  made  in 
the  trachea,  and  a  small  pipe  introduced,  through  which 
the  air  may  be  applied  by  the  aid  of  a  small  bellows. 
These  remedies  should  be  promptly  applied :  as  death 
does  not  appear  certain  for  a  long  time,  they  should  be 
only  discontinued  when  it  is  clearly  affirmed. 

Although  much  more  might  be  said  about  the  hygiene 
of  mines,  and  many  rules  laid  down  for  the  miners  and 


134  MINE   VENTILATION.  §47 

bosses,  yet  that  belongs  clearly  to  another  subject ;  and 
this  would  not  have  been  inserted  but  for  the  frequency 
with  which  such  accidents  happen,  and  from  the  neces- 
sity of  applying  quick  remedies.  For  further  informa- 
tion, see  "Mine  Foreman's  Pocket-Book,"  issued  by 
T.  J.  Foster,  Shenandoah,  Penn. 


INDEX. 


Accidents  in  mines,  73. 
causes  of,  96. 
prevention  of,  92. 
decrease  of,  93. 
Acceleration  of  gravity,  22. 
Action  of  choke-damp,  11. 
of  white-oamp,  12. 
of  fan  and  furnace,  112. 
Adding  airways,  82. 
Adjustable  fan-shutter,  116. 
After-damp,  11. 
Air,  properties  of,  1. 
height  of,  2. 
weight  of,  3. 
analysis  of,  3. 
to  find  weight  of,  19. 
expansion  of,  19. 
motion  of,  23. 
boxes,  70. 
return,  73. 
stoppings,  74. 
splitting,  76. 

common  pressure,  in  mines, 
of,  85. 


Air  for  sanitary  purposes,  90. 
measurements,  97. 
quantity  per  horse,  91. 
quantity  per  lamp,  91. 
quantity  per  man,  128. 
Airways,  perimeter  of,  42. 

sectional  area  of,  42. 
different  lengths  of,  59. 
addition  of,  85. 
enlargement  of,  92,  97. 
Anemometers,  99. 

varieties  of,  99. 
Aneroid  barometer,  105. 
Area,  42. 

and  quantity,  61. 
Arnold,  Mr.,  98. 
Asphyxia,  treatment  of,  130. 
Atkinson,  Sir  John,  47,  49. 
Atmosphere,  thickness  of,  1. 
pressure  of,  2. 
variations  of,  27. 
Barometer,  discovery  of,  2. 

correction  for,  104. 
use  of.  106. 


136 


INDEX. 


Barometer,  sudden  fall,  106. 
Belgium  Commission,  37. 
Bends  in  airways,  41,  79. 
Berad,  4. 
Black-damp,  9. 
Black  Hole  of  Calcutta,  9. 
Blood,  circulation  of,  9. 
Blowers,  15,  76. 
Blown-out  shots,  94. 
Boty  safety-lamp,  36. 
Box,  Mr.,  129. 
Brattice,  wooden,  69. 

cloth,  70. 

Briam's  anemometer,  100. 
Buddie,  Mr.,  30,  76. 
Candles  in  mines,  30. 
Carbonic  acid  in  atmosphere,  1. 

exhaled,  8. 

composition  of,  9,  90. 

diffusion  of,  10. 

properties  of,  10. 

sources  of,  10. 

fatal  nature  of,  11. 
Carbonic  oxide,  12. 

fatal  effects  of,  13. 
Centrifugal  ventilators,  110,  115. 
Changes  of  temperature,  28. 
Champion  ventilator,  111. 
Chesterfield  and  Derbyshire  Insti- 
tute of  Mining  Engineers,  113. 
Choke-damp,  9. 
Circular  airways,  43. 
Clanny  safety-lamp,  31. 
Coal-dust  in  dry  mines,  95. 


Coal-dust  explosions,  94. 
Co-efficient  of  friction,  47. 
"Colliery  Guardian,"  94. 
Colliery  warnings,  108. 
Comparative  economy  of  furnace 

and  fan,  117. 
Comparison  of  fans,  111. 

of  air  and  gases,  4. 
Composition  of  air,  3. 

of  black-damp,  9. 
of  white-damp,  12. 
of    sulphuretted  hy- 
drogen, 13. 
of  fire-damp,  14. 
Compressed  air  in  mines,  69. 
Contractions  in  Airways,  97. 
Correction  for  anemometer,  100. 

for  barometer,  104. 
Cost  of  ventilation,  91,  118. 

by  fan,  92, 118. 
by  furnace,  92, 

118. 

Darlington's  testimony,  37. 
Davy's  experiments,  15. 

lamp,  32. 

Daubisson,  M.,  53. 
Defective  ventilation,  10,  17,  73. 
De  la  Roche,  M.,  4. 
Deputy  lamp,  37. 
Design  of  ventilation,  97. 
Detection  of  fire-damp  with  can- 
dle, 30. 

Detection  of  fire-damp  with  safety- 
lamp,  39. 


INDEX. 


137 


Diagram  of  engine,  101. 
Dip  ventilation,  28. 
Discharge  through  pipes,  54. 

through  thin  plates,  54. 
of  gas,  95. 

Distribution  of  air,  73,  84. 
Division  of  air,  77. 
Doors,  74. 
Drag  in  mines,  44. 
Drift  measurements,  102. 

ventilation,  69. 
Dunn,  Mr.,  129. 
Duty  of  miners,  92. 
Economy  of  furnace  and  fan,  120. 

of  splits,  80. 

Effective  horse-power,  103. 
Efficient  ventilation,  96. 
Efficiency  of  fan,  109. 

of  furnace,  109. 
Eloin  safety-lamp,  36. 
Enlargement  of  airways,  92,  97. 
Estimating  air  for  mines,  88. 
Expansion  of  gases,  19. 
Experiments  with  anemometer,  99. 
with  fan  and  furnace, 

117. 

with  fire-damp,  15. 
with  safety-lamps,  37, 

38. 
Explosions,  92. 

indications  of    (theo- 
ry), 108. 
Face-airing,  71. 
Fan,  impediments  to,  28. 


Fan,  hand,  69. 

economy  of,  92,  118. 
drift,  103,  112. 
Guibal,  115. 
Waddle,  116. 
useful  effect  of,  116. 
sizes  of,  117. 
shutter,  117. 
experiments,  119. 
Faraday's  estimates,  7. 
Fire-damp,  14. 

•      Davy  on,  15. 
discharges  of,  16. 
detection  of,  39. 
Fire-proof  brattice-cloth,  70. 
Force,  estimation  of,  44. 
Formula   for   cubic   foot  of  air, 

20. 

for  total  pressure,  50. 
for  pressure,  50. 
for  motive-column,  26, 51. 
for  water-gauge,  52. 
for  quantity,  52. 
for  units  of  work,  52. 
for  horse-power,  52. 
Formulas,  49,  121. 
Foster,  T.  J.,  129. 
Frankland,  Dr.,  3. 
Free  fall,  22. 
Friction,  41. 

and  area,  43. 
co-efficient  of,  47. 
to  overcome,  44. 
and  pressure,  59. 


138 


INDEX. 


Friction  and  power,  55. 

dependent  on,  59. 
and  velocity,  61. 
and  water-gauge,  68, 112. 
Furnace,  principle  of,  24. 
position  of,  24. 
power  of,  27. 
economy  of,  92,  118. 
danger  of,  109. 
Galileo,  2. 
Galloway  Royal  Society's  Journal, 

39. 

Gases,  specific  gravity  of,  4. 
nitrogen,  5. 
oxygen,  7. 
carbonic  acid,  9. 
oxide,  12. 

hydrogen  sulphide,  14. 
marsh-gas,  14. 
hydrosulphuric-acid  gas,  14. 
proto  -  carburetted      hydro- 
gen, 14. 
light  carburetted  hydrogen, 

14. 

hydride  of  methyl,  14. 
expansion  of,  19. 
chief  characteristics,  19. 
Gay-Lussac,  53. 
Goodwin,  Mr.,  128. 
government  warnings,  108. 
Gravity,  action  of,  22. 
Guibal,  M.,  experiments  of,  99. 
fan  experiments,  113. 
fan,  115. 


Guibal,  M.,  fan  in  United  States, 

117. 

chimney,  116. 
Gunpowder,  94. 
Gunpowder,  charge  of,  96. 

use  of,  96. 
Hall's  lamp,  36. 

report,  94. 
Hand  fans,  69. 
Head  of  air,  25. 
Headings,  72. 
Heart,  action  of,  9. 
Heat  of  shafts,  24. 
Hedley,  Mr.,  129. 
Horse-power,  52. 

effective,  103. 

nominal,  103. 
Hot  air,  23. 
Howe,  R.,  113. 
Hutch inson,  Mr.,  128. 
Hydrosulphuric-acid  gas,  14. 
Improvements  in  safety-lamps,  34. 
Illuminating  power  of,  36. 
Improvements  in  ventilation,  73. 

in  fans,  110. 

Indicated  horse-power,  101. 
Indicator-cards,  103. 
Inertia,  41. 
Influence  of  air,  5. 
Injustice  to  men,  96. 
Inspectors,  92. 
Irregular  airways,  85. 
Large  airways,  92. 
Laughing-gas,  6. 


INDEX. 


139 


Laws  of  air  in  mines,  53. 

of  ventilation,  92. 
Le  Blanc,  10. 
Liability  of  miner,  93. 
Limits  of  velocity,  89. 
Lundhill,  73. 
Lungs,  action  of,  8. 

capacity,  130. 

Measurements  of  air  by  anemome- 
ter, 99. 
fan,  101. 
of  air,  97. 

Mackworth,  H.,  129. 
Magnus,  53. 

Managers'  ignorance,  92. 
Maps  of  ventilation,  4. 
Mariotte's  law,  2. 
Marsh-gas,  15. 

properties  of,  15. 
explosive  mixtures,  15. 
Mercury,  weight  of,  15. 
Meyer,  Dr.,  12. 
Miners'  asthma,  11. 
Mines  with  one  orifice,  69. 
with  two  orifices,  72. 
Momentum,  41. 
Morison  safety-lamp,  38. 
Motive-column,  25. 

calculation  of,  27. 
Movement  of  air,  23,  43. 
Mueseler  lamp,  35. 
Murphy  fan,  111. 
Natural  ventilation,  23. 
Nitrogen,  5. 


Nitrogen  compounds,  6. 
Nixon  ventilator,  110. 
Nominal  horse-power,  103. 
North  of  England  Institute,  38, 116. 
Oxygen,  7. 

necessity  of,  8. 

consumption  of,  9. 

starvation,  11. 
Orifice  of  discharge,  54. 
Parish  safety-lamp,  36. 
Peclet,  53. 

Pennsylvania  mine  laws,  129. 
Perimeter,  42. 
Permanent  stoppings,  74. 
Phillips,  Professor,  129. 
Pneumatic  paradox,  26. 
Poisonous  gases,  10,  12,  13. 
Position  of  downcast,  24. 

of  fan,  28. 

of  upcast,  28. 

of  furnace,  24,  28. 
Power  of  winds,  29. 

increase  of,  56. 
ventilating,  55. 
Pressure  of  air,  2,  85. 

and  water-gauge,  46. 

total,  50. 

per  square  foot,  50. 

ventilating,  54. 

defined,  55. 

and  length,  57. 

and  perimeter,  57. 

and  area,  58. 

and  friction,  59. 


140 


INDEX. 


Pressure  and  volume,  61. 
Prevention  of  explosions,  92. 
Problems,  124. 
Properties  of  air,  40. 
Proto-carburetted  hydrogen,  14. 
Quantity,  formula  for,  52. 
and  area,  61. 
and  development,  76. 
for  mines,  88. 
Rebreathing  air,  9,  91. 
Regnault,  53. 
Regulators,  74,  76. 

to  find  size  of,  83. 
Reports  of  North  of  England  Ins- 
titute of  Mining  Engin- 
eers, 38. 
of  Belgium   Commission, 

37. 

of  Chesterfield  and  Derby- 
shire, 113. 
of  Mr.  Hall,  94. 
of  N.  Wood,  37. 
Resistances  to  circulation,  23. 
Richardson's  estimate,  91. 
Risca,  73. 
Rubbing-surface,  42. 

and  friction,  47. 
Safety-lamps,  discovery  of,  31. 
improvements,  34. 
varieties,  34,  93. 
illuminating    power 

of,  36. 

reports  on,  37,  38. 
use  of,  39. 


Scientific  ventilation,  88. 
Single  air  currents,  77. 
Shaft,  ventilation  of,  24,  69. 

temperature  of,  '24. 

position  of,  28. 
Shot-firing,  96. 
Sliding  shutters,  76. 
Specific  gravity,  4. 
Spiral  fan  casing,  117. 
Splitting  the  current,  76. 

advantages  of,  79. 
effect  of,  82. 

South  Shields  Committee,  37. 
Steam- jets,  28,  109. 
Steel  mill,  31. 
Stephenson,  Sir  George,  32. 

lamp  of,  32. 
Stoppings,  74. 
Struve  ventilator,  110. 
Stythe,  9. 

Sulphuretted  hydrogen,  13. 
Sulphuric-acid  gas,  14. 
Sulphuric  ether,  98. 
Table  for  specific  gravity,  4. 

for  weight  of  air,  21. 

for  velocity  of  winds,  29. 

for  water-gauge,  46. 

for  square   root  of    water- 
gauge,  68. 

for  air  pressure,  107. 

for  Guibal  fan  experiments, 

115. 

Tarred  brattice-cloth,  70. 
Temperature,  variation  of,  2,  27. 


INDEX. 


141 


Temperature  and  friction,  48. 

and  barometer,  106. 
Temporary  ventilation,  70. 
Thick  seams,  advantage  of,  96. 
Thomas,  J.  W.,  10,  16,  49. 
Throat  of  fan,  117. 
Torricelli,  2. 
Total  pressure,  50. 
Units  of  work,  52. 
Upcast  shafts,  24,  28. 
Useful  effect  of  air-boxes,  71. 
of  engines,  103. 
of  fan,  101,  116. 
Velocity  of  air,  29. 

theoretical,  23,  47. 
and  head,  47. 
and  pressure,  54. 
and  friction,  61. 
Vena  contracta,  54. 
Ventilation,  23. 

natural,  24,  69. 
furnace,  24. 
laws  of,  53. 
pressure  of,  54. 
power,  55,  103. 
shaft,  69. 
drift,  69. 

cost  of  increasing,  77. 
economy  of,  88. 


Ventilation,  cost  of  91. 

of  fiery  mines,  90. 
arrangements  for,  91. 
measurement  of,  97. 
mechanical,  110. 
water-fall,  110. 
Volume  and  pressure,  53,  61. 
and  length,  59. 
and  area,  60. 
and  perimeter,  60. 
and  rubbing-surface,  60. 
Water-gauge,  44. 

use  of,  45. 
as  a  check,  45. 
and  pressure,  46,  68. 
formulas  for,  52. 
table  of,  68. 
and  fans,  112. 
Weight  of  mercury,  3. 

of  black-damp,  9. 
of  fire-damp,  14. 
of  air,  19. 
of  water,  44. 
White-damp,  12. 
Williamson's  lamp,  36. 
Winds  an  impediment,  28. 

velocity  and  power  of,  29. 
Wood,  Mr.  N.,  37. 


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FED  2  1920 
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SEP  5  1924 


